It's weird, because I change my avatar a lot but always to the same things... so does that even count??? My sig I just updated for the first time in like a year, but again, same exact layout the theme. So idk? Six in one half a dozen in the other??
Pre-2015 I would change it every month at least because back then I would be obsessed with an anime/manga/TVShow/music/etc and based around my avatar and sigs on that. 2016 and after it's now usually every few months fastest, though sometimes I can stick to an avatar and signature 5+months.
During my first five years, I changed both a lot. Whenever I got a hold of something to make a tag out of with my shoddy GIMP skills, a new avatar and signature was bound to appear. Then I went through a phase of using three icons in the signature, and it was pretty much the same deal.
Right now, though, I like my current avatar. The avatar I chose right when I came back was my SDV character, but when I saw my old graphics thread I just reused what I already made, haha. As for my signature, it changes a lot, but I like the minimalist approach I have going atm. It evokes the same feeling as my signature during the six years I was away.
Being part of many fandoms + being easily excitable doesn't make it easy to settle on a single profile. On PC, I've finally found a flair/avatar/sig combo that I'm actually happy with (thanks to Fairy), so now I'm set on this being my PC profile (or theme at least).
Anyone who's seen me on Discord though knows how often I change my avatar. I suppose it's the perfect counter-balance to PC; whenever I'm in the mood to change, I should just focus on Discord instead.