The policy has always been that I don't change user names unless there is very good reason like a typo, used your real name etc.
Part of the reason for that is is it gets a little confusing for members and they don't know who is who after seeing the same name for months or even years. Also I don't want to be bombarded with requests but I'll also understand many may have registered with a name without realizing they would be here for a while and that name no longer makes sense.
Having said that I'll now take requests for a one time name change for those with more than 250 posts. Just PM if you want it changed. If your going to request this carefully think about what you want, it's only one time deal.
So I don't have to repeat myself this will be the process, once I get the request I'm going to change it. You'll get logged out and you'll have to login with your new name. If there is any issues that arise you can use the "contact administrator" link at the bottom.