dan - I know what you mean, because it was the same for me: I picked a username pretty much on the spur of the moment so I could post, and three and a half years later, I’ve still got this greasepaint moustache. 
A from-the-inside view: for me, at this point, to change my username would feel like I was going into the Witness Protection Program. This name and I have built up an identity of sorts - it’s how people know who I am in this corner of cyberspace. It would be a very strange thing to change, even if I liked my new name a lot better.
From the outside perspective, even simple name changes can be confusing. For instance, I think Stuffy is the former stuffinb, but I’m not 100% sure. (I keep meaning to ask.) And when it’s to a totally different name, I’m generally totally thrown. (I wish I could remember who Hello Again and Why A Duck were before they took on those names.)
So I’ll vote for “don’t change”. I feel like I’m getting to know who you are, at this point, and I don’t want to start over from scratch, which is what it always feels like when someone changes their name.
And thanks for including me in your sig! 