When is Duolingo . . . . . too much?
So I've been going for years, and I'm very familiar with the vocabulary on here.
So I'm wondering when it's time to say goodbye to the English -> German tree. I'll keep doing the English tree, but I want to do Busuu too. Kind of a switch off until I finish Busuu, then I'll find another resource.
Have I graduated Duogerman?
Duolingo can never be too much!
In all seriousness, if you realize that you have exhausted this site's resources, then it's fine to move on. Perhaps you will continue to gain more understanding of a language when you transition to an advanced site (if that's what Busuu is).
I also suggest clozemaster, if you haven't used it already.
When you feel you're not learning anymore, it's time to move on.
I'd recommend Lingvist -- I haven't done their German, but their French really boosted my reading comprehension and vocabulary. It's unfortunately not as much fun as Duolingo, but very effective and a sleek, free website and app(s).
In addition to the other suggestions, I'd like to recommend using the language (not just for the purpose of learning).
Go to forums whose topics are of interest to you, see what people have written, and try to express your opinion.
I think we as language learners often circulate around "learning languages", but it can be totally interesting to make use of the newly acquired skills to achieve something outside of the scope of languages.
Just as an example: There is a wonderful site/forum on the topic of maths: http://matheplanet.com/ (Also covering physics, IT and other topics).
Or cooking: http://www.chefkoch.de/forum/
Just as ideas. Once upon a time, I was interested in Karate, and I read (and, to a much lesser extent, wrote) in a Karate forum (in English). This not only helped me understand the art, but also the language. Win-win. ;-)
If you've been going for years, it's long past the time you need to get out and start speaking to people. If you don't have any German speakers nearby, sign up to a language exchange site like Italki and find either a tutor or a language exchange partner.
There's nothing that will improve your language skills more rapidly than regular speaking practice.
Generally I think that duolingo is a start for a language, once you Finnish a tree it does not actually mean that you are fluent. Go pick up a german book, visit Germany, see how much you can use your language, there is always room to improve. Anyway, you can always do both. Use duoligo for your next language while you use Busuu for your german, if you think you learn better with one or both or many do that, this for you and your language. If you don't think you can do more german with this try something else. I wish you luck.