I've had tanks continuously since I was 18 and in college, so that's 15 years. Bettas I've only liked for a few months now.
For most of those 15 years though I was pretty ignorant of proper fish care. I've really only gotten into it big time over the last year or so. I've gone through a lot of goldfish and related fish, and now have a 55gal tank with otos, guppies, skirt tetras, and bosemani rainbows. I also have a 20g betta sorority and a lone giant HMPK (baby) in a 10g in the kitchen. I do lots of water changes - payback for all those years when I didn't do enough!