I think I won't have to "consider" leaving osu!, it will just happen naturally at some point. I mean, there are some games which I like very much, but there were times when I looked at the shortcut on my desktop and thought "Wow, I can't believe it, but I haven't played that game in almost a year!? After all, this was one of my favorite games, but I just sort of... forgot about it! What the hell happened?!?"
Perhaps something similar will happen with osu as well.
I never stress about stuff like that because I always play whenever I feel like it. Never really called it quitting, more of an hiatus. So yeah, I'll probably never quit, will just have moments where in I wouldn't play it for a long time, since forever is quite a long time.