It's a single time, after patches that happen every few months. Not sure it's worth coding in a change for something that the staff WANTS their players to see (ie: things changed here, please read this so you don't bother me asking if it changed).
This is only shown to players with the addition of a patch to the server. Turning it off for one player disables it for the whole account. Just find the check box at the bottom of the window. As not everyone checks the forums actively, or even the main website it is important for us to notify players regarding changes to the server.
