TPAM is probably right. I've changed my avatar a fair few times over the years but in the end I'm keeping this one for the foreseeable future. It might just be as old as my membership (possibly older) but I'm mainly keeping it because of the avatar-username synergy.
Well, it definitely predates your registration, TPAM, but I've changed it quite a bit since then because of the Movie Theme of the Week. As of the past two or three years I decided I might as well stick with this particular avatar.