By the way, can anyone whom usernames have changed, tell us how did they apply for the change in username and how long did it took to get the application successful?
It can take days, weeks, months, years, or even NEVER. You just need to PM the admin with a good reason and hope for the best. The speed is determined by your reasons, and being an established member is advantageous. (Change of username is one of the most difficult requests)
It took a few days for mine to be approved. I was fortunate.