what happens if I change minimum user name length from 3 to 6?

[rnmcd]

what happens if I change minimum user name length from 3 to 6? Will anything happen to the users that have the 3 character names?

[Lats]

Will anything happen to the users that have the 3 character names?

No, they're safe

The username only gets checked at registration time (that I could find).

[rnmcd]

I just want to make sure that the users that created the 3 letter names aren't required to create a new 6 letter name if I change the minimum username length.