How many times are we allowed to change our account name?

I just have my account name changed for the first time and I wonder how many times I can do this? Is there a limited time a player is allowed to change their account name in their life time? or is there a cool down like once every 3 months?

IMPORTANT:
Also do you keep a record of what account names the players initially created their account with and what account names they may have changed to in case you need to verify ownership for account recovery purposes?

If there is I need to note down my account names.