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According to YouTube Studio my videos typically get a weird gigantic spike in watch time after they've been up for about half a year. The one that's become the most watched coffee roasting video that actually provides good information on that site didn't get much for views in its first year. Now I just tell people to watch my stuff on https://video.typica.us/ but nobody does. 
The staircase is a pretty common pattern on the stuff where I'm trying to provide useful information. I put it out, nobody notices that it exists, but then half a year, a year, two years, five years later someone happens across it, shares it with a bunch of people, and it gets popular.