Depends on the hobby. I tend to collect hobbies and then grow bored of them, then return to them a while later.

I’ll become absolutely obsessed with learning about “hobby x”, and spend two months basically getting as close to an expert on it as I can with self-teaching. (Video Editing, filmmaking, screenwriting, 3D modelling for flight simulators, Graphic Design, etc…)

Then I’ll grow bored and move onto a new obsession from the above list, focus on that long enough that at least 25% of my knowledge of the previous obsession vanishes and I have to relearn a bunch the next time that obsession rolls around.

I’ve been told that’s possibly ADHD, but since I suffer from depression I’ll take my bursts of obsessiveness over lack of any motivation any day.