I change mine usually weekly or after 4-5 days. What about you?

Rarely. I change my sig more often than I change my avatar.

NEVER! This avatar will follow me forever xDD. I even use it for skype with my friends :P

My tendency to build schedules for meaningless things means that i change my avatar every year, on the year. I have had 5 so far; T-Bone, Jaimie, Sogeking, General Gum, and now Princess Luna

I change my signature on a rotating schedule that usually runs about 5 a year.

Year 1: About Me, Afro Luffy, Sogeking, Metroid: Other M, Games of 2009.
Year 2: SWAT Kats, Pokemon Soul Silver, Nintendo Trifecta, Urd, Platformers of 2010.
Year 3: Megas XLR, Pokemon White, Wii U, Queen's Blade, Super Mario 3D Land.
Year 4: Straw Hat Reunion, Trip to Japan, Moar Mario, Luna & Fluttershy, New Super Mario Bros U.
Year 5 (so far): General Gum, Monster Hunter Tri Ultimate, Nintendo Direct

Last time was around 2 years ago I think. I don't change avatars because people stop recognizing you.

I'm also paranoid someone will steal my avatar too, it's just that good.

It depends on how badass the avatar is. Normally, I change it every 2-4 days, but this Banekitty avatar will stay for a little longer.

Edit: Banekitty is gone..

Whenever something cool gets announced.

I have used the same avatar since xmas day 2007

Whenever i feel like it, i had the first one for months and i've had others for only 2 days...

Years usually. I've only made two that I use on forums.