There's probably no use keeping them on your blist more then a week, they'll either be deleted to create a new character or banned and on a new account.
Yeah it's a lot to clear though. Would just be nice for them to implement a filter because it would solve the whole gil spam issue and no one would have to worry about blacklisting/cleaning blacklist. Also wouldn't have to sit there and report because you would never see them once you had your filters set up.