I've got one I still ride a few times a year. LIke
@elemmac, I started around 12 (1971!).
For awhile, I rode it out to the irrigation pump every time I needed to mess with it, but now we're on a pressurized line, so no more pump, and I realize now that I didn't ride it all last year.
I put a knobby tire on it once and went on some mtb trails, but that was dumb, because, well, NO COASTING! Kinda sucked the fun out of that idea.
Unicycles will definitely improve your balance for unicycling, but I'm uncertain about much transfer to other activities.