I tell people that you should never get more than 100 day streak. If you have not reached the end of duolingo in 100 days, then you should give up as you are not putting enough time into study to ever learn the language, while if you finish the tree in 100 days you are ready to move on.
Obvious 100 days is somewhat arbitrary, but it is a good round number to work with. If you reach 100 days you should at least stop to evaluate your real progress: If you are not at least mostly done with the tree you should be honest with yourself that you are not motivated enough to learn the language. If you are mostly done, then 100 days is a good time to start looking for other ways to engage with the language.
Obvious 100 days is somewhat arbitrary, but it is a good round number to work with. If you reach 100 days you should at least stop to evaluate your real progress: If you are not at least mostly done with the tree you should be honest with yourself that you are not motivated enough to learn the language. If you are mostly done, then 100 days is a good time to start looking for other ways to engage with the language.