Makestation

Pretty self-explanatory.

Personally, I change mine every 6-12 months. What's your vote?

I usually change my avatar when I feel like it, wether it would be once every 2 weeks or every year

I should add "when I feel like it" to the list haha.

I've had less than ten avatars in the 3 1/2 years I've been active on forums.
I changed often at first then I settled on a picture of locomotives, then I changed to a cow, then I changed often, then I found emu and haven't changed my avatar in over 2 years now.

I'm the same way personally. I tend to change avatars quite frequently finding one I like, but once I get one I like I just leave it for a while.

I don't have an avatar on any sites anymore

Personally I prefer not to use an avatar, unless admin asks me to.

I never really change my avatar a lot. I think my posts are more important than my avatar.

Agreed. I mostly use an avatar just to make myself easy to recognize on forums, but in the end it's really not that important in the grand scheme of things.