I understand viscerally this comment about something becoming a source of stress. Actually a couple of apps have done this to me in the past, and I immediately reject them (by uninstalling them) when I recognize that the app is using the anxiety and stress to twist the screws and get me to pay for something. Fuck that. I'm curious here, though. Except for not having an exceptionally long streak number associated with your username that you have earned, what penalties exist for not maintaining your streak? Does Duolingo like cut you off from completing lessons or otherwise impose restrictions on using the app if you don't maintain a streak?
Also, I've been putting a lot of time in the Russian module and I'm really disappointed that there's no way to learn the grammar rules in Duolingo. Russian especially has surprising behavior depending on the characters used.
So as I stated, Duolingo's value for me is the gamification of getting me to study Russian on the daily bases. BTW, I have used it for 2-3 years now. I've had various streaks of 50 days, 100 days, etc. I'm 1-2 days now from 200.
To answer you, when I went off grid for camping, I lost my steak. But that was it. I just had to start from zero streak again. However, my Russian lesson progress stayed where I left off.
There is (used to be) this power range under each level that you completed. And if you do not use the app for while, they gradually lose their power strength level. It's a way to ensure you return back to old lessons and you repeat them. But still does not effect your lesson progress.
At the end, Duolingo was a free (I actually paid a few times to retain my streak, so probably have paid them about $20 or more by now) way for me to have a structured/organized path to learn Russian with a motivator. I always find ways to complete my daily Russian lessons even in busy days. I think if the streak was not a factor I would have probably given up on that a while ago.
If you really want to learn Russian you have to get more resources. Often when I googled some word = "russian grammar" I found an online source or class that explained which was very helpful. RussianPod101 has some free podcast lessons that is good to help you with pronunciation and also some common phrases. But you still need a proper grammar book to make it through it all.
Also, I've been putting a lot of time in the Russian module and I'm really disappointed that there's no way to learn the grammar rules in Duolingo. Russian especially has surprising behavior depending on the characters used.