IF your really concerned about the controller disconnecting while it sleeps contact Square Enix about it....there is also a lengthy thread about this in the Japan forums.....

Because I exclusively use this controller for all my games and FF I sent SE a ciustomer complaint on it, many have said
that it did work initially but it's probably something that they changed in the FF Config program they just need to fix it.

All the games, yes ALL the games that I play you can reconnect the Pad by just pressing the X...except for this game, it's very annoying.