In my opininon, there's no an "after" with Duolingo. It never ends.
I had an stroke of 420 days. I lost it because a family issue and now I have one of 140.
Duolingo is not the best way if you want master a language. Probably you can reach a level between A1-A2. But practicing every day you are sure you reinforce basic structures and vocabulary. The little daily effort worths. And the point is to do it without thiniking about it.
Besides, after all this time, I still find some new things, because Duolingo team introduces new sentences, structures and words continously. And recently they introduced a new structure (by now, not for all users, but they plan extend it for all of us) based in different levels inside every lesson. They call it "crowns". I'm not sure if it is a good idea or it can motivate students more.
Furthermore, reinforcement button makes you work with your weakest parts. When you finish the tree, you can choose this option.
And finaly, when you practice in your computer instead your smartphone, reinforcement lessons are differents, and the way you do it (for example, against the clock) makes you think in a different way.
I still use Duolingo, still do mistakes and still learn, although I'm not learning as much as I would like. I'm considering giving up on it for now, and switching to some other tools (apps) that I could use to take up the void that it'll leave.
My streak right now is 911 days, so perhaps I'll hit 1000 and call it a day after that. I'll keep Duolingo installed and will surely pick it up again, when it's time to learn the basics of a new language. I'm still hesitant to call the new crown system an improvement; I feel like the dev team at Duolingo could have spent the time on other improvements instead.
Rob -- try out the "reverse tree" also. If you did the English-to-Spanish and you're feeling like there's nothing new to learn, do the Spanish-to-English course. It'll introduce some new vocabulary and a lot of annoyingly long sentences to translate. ;)
italki, of course :)
More seriously, Duolingo is a nice tool because it feels like a game and presents things to you in bite-sized chunks. I think it works especially well to give you a school language course-type experience (that is, translation-based) in a convenient app that motivates you to stick with it. And it works well for people who will research things like grammar rules on their own to support use of the app. It doesn't do especially well to train speaking or listening comprehension, or to "think" in another language. I used Duolingo for six months to reinforce a basic understanding of French, came to the end of what Duolingo offered me, and found that I didn't speak French. Oops! For that reason, I turned to italki to connect with live teachers who could focus on conversation, pronunciation, speech production and listening comprehension. I'm still working on it.
Well my story is large ( sorry I know that is the word) but I use doullingo for remember my grammar in English and after I try to learn Korean, It was a failure.
Then I saw korean dramas and I try to help with subtitles transcribing dramas in English, this help for understand how was my mistakes in English, but yes I still making the same mistake.
And I thounk to see Englis clas for remember all again, yes I felt frustrated because I knew that I know some things in English and see again Is worried for me. But my teacher this year recommended me this page and I help me for other people help with my writting and speaking, now I use this page and other page that I write with other people the corrects me and show me with x and ✓ how I write and how write well.
I don't think you need to move on Duolingo, but I understand you feel you're not making progress as much as before in a more advanced level. Still it can be used to keep vocabulary fresh!
I don't know how confident you feel in your target language, but you can use the words you learned to start developing your writing. The notebook section is perfect for that.
Besides, you can start listening to some podcasts or watching series, if you think you can do it.
Finding someone to practice would also be helpful. You can start chatting, skyping or even hire one of the tutors/teachers here to take your language learning further.