how long do @usernames take to refresh?

[threemeow]

hello. i changed my @Username on one of my youtube channels, but i realized i changed it on the incorrect channel. i changed it back, but on the correct account, it still says the username is taken.

when i type in the old username on the incorrect channel, it still shows me it.

how long will this take to refresh so i can change the name of the other channel to the correct name?

thanks!