I always had it in mind that if a day comes that I have nothing to write about I'll gladly just let the streak fall and just wait until the inspiration takes me to write, but luckily that hasn't happened yet.
Sometimes I write some in drafts as a backup, and a lot of the time I have a note book with post ideas for the days things ideas are slow.
A 600 day streak on duolingo is great, are you focusing on a particular language or do you bounce around a bit?
I have been trying not to worry too much about posting as I want it to have value when I do. I do some short stuff on Snaps and Waves.
I'm doing French on Duolingo and may understand it better than I did when at school. I have needed to use some 'freezes' when I could not do a lesson or just forgot.
Back in school I was never interested in learning another language, but as I got out of it I became really interested in it. I've picked up a bit of Spanish, but not enough to hold even a basic conversation, but I do find it cool that I know enough to ask for stuff.