On the Mojang Support page it says that if you change your username the old one will stay locked for 37 days. You can change your username 30 days after you last changed it. This gives you a week to decide whether or not you want to go back to your old username.
Does this only apply the first time you change your username, or every time that you change? Also, does it only keep the username you're changing from, or the initial account name?
Best Answer
This applys to each instance where you change your username. While your old username becomes available to other players after the 37 days, there is still reference to the old username on your account, for identification purposes.