What to do after "learning" a language to not lose it?

Hi there!

I tell you a little bit of my background. I
have always liked studying languages and this is my current level:

Catalan: native

Spanish: native

English: Cambridge proficiency level (C2)

Japanese: JLPT Level 1 (got it more than a
decade ago...)

Chinese: HSK 5 passed

Russian and Korean: Learning for fun, advanced
beginner or low intermediate I would say.

I am 37 seven years old, I have a full-time job that has nothing to do with languages and also spend a lot of time taking care of two old relatives. So, I struggle A LOT trying to maintain these languages alive. That has made me wonder what everyone else does to keep their languages alive. I cannot do a career change and I have no chance to travel / live abroad. What I currently do is reading a lot, but I would love to find some activity / study method to keep all those languages alive. I used to be a Ted Talk volunteer translator but stopped when they changed the platform.

I am a bit discouraged because I put a lot of effort and time in learning those languages and I don't use them for anything but personal reading.

Any ideas? TIA!