This always creates a load of forum threads as soon as a server/shard goes down. With so many different time zones being on the game at once picking a time to go offline will be a sensitive issue. More so around the time new content is introduced as some countries are going to be asleep when it goes live.
How long do you think server maintenance on a shard of this scale will take once it's a live game, and how often will they be needed?
I know we're a long way off worrying about this but it will come up sooner or later.