I am especially curious about experiences and advice from “non-professional” learners.
Myself, I come close to a limit with 5 languages next to a full-time job in a non-foreign language related domain. My native language is German. We speak it at home. Living and working in the Netherlands the language at work is Dutch. I get listening and reading practice in English every day. From time to time I add in a novel in Afrikaans (or I listen to the audio), often stories written by the South African writer Deon Meyer. The books have an extra dimension and authenticity in the original text because characters switch code between Afrikaans and English, mixing in some Zulu words. My focus as a learner is on the French. I try to get daily news from French media sources, have regular meetings with an Italki tutor and use various internet tools. I try to integrate language learning in daily activities on my way to the work, during cooking or gardening. Because I feel a passion for Italy I wish to improve in the Italian language but I realize now that my progress remains limited because I simply cannot really fit in more languages in my daily routine. Not to talk about refreshing languages I studied before without having achieved a conversational level. (Russian, Korean) Many of you keep up a high level (B2+) in multiple languages. I am curious to know more about your personal strategies. Could you share some tips and tricks?
Of my 12 languages I can speak 5 at a professional level (Spanish, English, Catalan, Italian and Portuguese). Other 3 languages (French, Romanian and Basque) I can speak at semi-professional level (B1 level). I used to speak Galician at B1 level but now it’s rusty. The other 4-5 languages I speak (Greek, Turkish and Hebrew) I can speak them conversational tourist (A2 level).
Probably helpful is also to use more than the mother tongue at home. Many Polyglots do not speak their native language all the time at home, but live with people that speak other languages or also learn other languages, so that one can speak those on a daily level. I am not sure if that is possible for you, but certainly sounds another option to the great things you are already doing. 
Indeed. My parents are monolingual in Spanish, with a bunch of English, Hebrew and Yiddish words (I’m an Argentine Jew). So I need to socialize, and to find language partners and/or language environments all the time in order to maintain my languages as fresh as possible.
I started to use Italki to improve my spoken French. The paid language tutor works better for me than the search for mutual language exchange. It proved not that easy to find a good match to make an equal exchange possible. How do you find language partners? Could you establish longer lasting conversation partnerships after polyglot events?
I used to go to Mundo Lingo Buenos Aires three times a week until the pandemics began in March. Having fun, drinks, and 350-400 people from 30 different countries that speaks 50 different languages So I really need those events.
What’s a “high” level??
If you mean a C-level then I have 3 languages on that level: My native German plus Dutch and English. For both Dutch and English I have language diploma’s and in Dutch even I did studies by letter correspondence at “Leidse Onderwijsinstellingen”.
Last year I participated in the Polyglot Gathering for the first time. Afterwards, someone had found out my email and suggested a language exchange (Hungarian - Slovak). We’ve been corresponding in these two languages for over one year, and today we had our first Skype session. It does work and motivates.
I think once you passed a certain level, you don’t really have to do much to maintain your languages at a high level. Of course, it’s good to read something or listen once in a while, but even if you haven’t been using these languages for years, you’ll get back to them very quickly. Of course, you might lack some words, but you are able to paraphrase them and have a fluent conversation anyway. So I don’t really care much about my C languages, but concentrate on A languages, which I’d love to get up to B!
I am fortunate enough to be in a profession (university/academic research) in which people from the whole world are involved and so I can combine my interest in languages with my work. If I use my languages practically I am maintaining the language skills which are useful for me.
Hallo @Ron. Ich antworte jetzt in deiner / Ihrer Muttersprache. Ich arbeite als Technische Redakteurin, und ich muss meistens auf meiner Muttersprache Englisch arbeiten. Jetzt überarbeite ich mein Finnisch, um meinen Wortschatz zu erweitern. Ich möchte auf einem C1-Niveau meine Sprachen zu sprechen. Wenn ich zu schnell lerne, vergesse ich es. Fünf Sprache ist ganz genug, wenn jemand wenige Zeit hat. Meine Arbeit ist kognitiv anspruchsvoll, und ich habe oft niedrige Energie davon, weil ich täglich tief recerchieren muss. Schritt für Schrittt.
Ich habe auch Englisch als Muttersprache, und benutze vier andere Fremdsprachen in meiner Arbeit (Deutsch, Niederländisch, Russisch und Polnisch), also sind wir beide bei fünf Es ist doch schwierig, Zeit für Sprache Nr. 6 zu finden… ich würde sehr gern Tschechisch oder Französisch besser sprechen, aber mir fehlt die Zeit und Energie um mich zu bemühen, den Niveau von beruflicher Kompetenz zu erreichen… wenn ich dienstlich eine Email auf Tschechisch fassen würde, bräuchte ich 3 mal so viel Zeit. Wenn ich meine Zusammenarbeit mit Tschechen intensiviere, bin ich vielleicht bereit, mir die zusätzliche Mühe zu machen
How do you find language partners?
Ich habe mich bisher selbst nicht wirklich bemüht, einen Sprachpartner zu finden, aber mich kontaktieren manchmal Leute über Sprachlernseiten (vor allem Russen und Chinesischsprachige), um mit mir Japanisch zu lernen, und mit denen muss ich dann einfach ihre Sprachen sprechen, weil sie noch nicht so gut Japanisch können (wenn sie schon gut Japanisch können, dann spreche ich in der Regel nur Japanisch). Das ist kein gleichmäßiger Sprachaustausch, aber bei mir hat es immer so funktioniert. Also, Freunde finden, mit denen ich meine Zielsprache notwendigerweise sprechen muss, war meine bisherige Methode sozusagen. Ein richtiges Sprachtandem wie “30 Min. Japanisch, 30 Min. Chinesisch” ist schwierig für mich 
Awesome!!! I would like to participate in a polyglot group. I feel all alone studying languages only by myself.
i’ve had a huge issue finding a language partner. i feel if i pay for a tutor i can worry less about frustrating them since they are being paid to listen to me. i have feared that a exchange partner would be less inclined to be patient. (even though the community gives me no reason to believe that they would be nothing but patient)
Ich denke, diese Konferenz ist die beste Gelegenheit dafür. Beginn einfach ein Thema, z.B. Wer lernt noch Sprache X und möchte gern in einer Gruppe lernen?
Oder die andere Möglichkeit, such dir hier jemanden, der Spanisch lernen möchte und eine deiner Zielsprachen spricht. Und dann frag einfach, ob der- oder diejenige interessiert ist.
I speak, read and write on a C1-C2 level: German, Italian, French and English. My Dutch is B2-C1 level – depending on the topics I have a C1-C2 level in speaking and writing.
In order to keep up with all 5 languages: I speak them every day – I have clients from a very diverse linguistic and cultural background: that helps! – also with friends and my family. We live in the Netherlands in a very international community where it is easy to switch between 3-5 languages per day, if you want. Also, I read a lot and try to balance between the languages. At the moment it’s more German books, but also Dutch ones. English is a must every day anyways, and French and Italian it’s on Mondays and Fridays – quindi, se fossi molto coerente, dovrei scrivere questo messaggio in italiano, oubien en français. 
Oui! Ce forum est génial. J’ai déjà rencontré des gens très intéressants et je peux apprendre des langues avec eux. Merci
Je crois que si on parle de atteindre un niveau avancé pour la première fois, ça demande beaucoup de temps et effort.
Au contraire, pour maintenir une langue active pour qu’on puisse la parler couramment, ce qu’il faut n’est pas exactement un grand quantité de travail focalisé, mais surtout des opportunités très fréquents de l’utiliser, même qu’ils soient assez brefs.
Si on se contente de maintenir les langues étudiées auparavant pour qu’on puisse les comprendre sans problème, mais on accepte qu’il faudrait un petit peu de “réactivation” pour bien les parler à la vitesse normale, alors je crois qu’il n’y a pas vraiment de limite!
I’m the same as you, Heidi. I learned Dutch to about B1-2 25 years ago, and I don’t need much time to revive it. I wish I had more opportunity, but I don’t. Auslan (C1) I can leave for years and pick up easily. Even French, which for me is A1, I don’t seem to lose comprehension of, but have to work at active expression now after 2 years of little to no speaking. The longer I learn, the longer I can leave it.