Almost never. It's my Icon for everything. Twitter, my personal Tumblr, Ustream, Fanpop, FanFiction.net, Youtube....etc. Sometimes I change it for like one Tag to something (normally PLL-related oder some other fandom) but it always goes back to this after a short time.
I usually change it fairly often. Like a Tag oder so, sometimes hours. But when I have an Icon oder an Bearbeiten that I'm proud of, I keep it for some time. Though I'm actually about to change my icon.