Im getting near the exp level you guys were at when you stopped using duolingo. Did you guys make any progress with your languages after you stopped?
Duolingo is for extreme beginner level learning only. It barely teaches grammar at all (unless you're in a well established language which has a lot of text descriptions written). For me I used it to get used to reading and basic vocab.
After that I moved onto various youtube series and blog posts, where you can find beginner and intermediate grammar lessons, but more importantly you can get deep dives into a very specific grammatical nuances that let you actually understand the real language.
Then after you have that intermediate grammatical foundation, you can focus on fleshing out vocabulary again using a flash card system (I use memrise) and also native material (shows, etc). The grammatical foundation will let you realize when you understand the structure of a sentence, which is fine even if you don't know all the words because you can just look them up and add them to your vocab list. But most importantly you can recognize when you understand the words but NOT the structure, which is something you should go look for a specific blog post about. And so on you learn grammar and vocab back and forth and you continue this for the rest of your life pretty much.
This is basically where I am getting to, duolingo has been my primary vocab and character familiarity resource, and then I use those lessons so I can jump into intermediate courses right away.
I do find it troubling that in my first month of learning Mandarin I was able to see some very clear grammar mistakes on duolingos end, but all in all I find its a good device for review and vocab.
So judging by everyone else's experience I should expect another few months of using it, max. ---