Of course. What would a timer on using the ultimate even look like? You meant cooldown?
Right, now I remember you could only use it once per day in Skyrim. Yeah, didn't expect something like that for ESO.
On topic, I don't think the disadvantages for being a werewolf or vampire are that big. +50% dmg from poison as a werewolf? Who's using poison anyway (well, vampires maybe with their mist form morph)? The weakness to fire for vampires seems more like a problem, but the decreased health regeneration is not that difficult to counter when you can svck everyone dry - and you can still get that passive that lowers the decreased health regeneration.
I think the best bet against werewolves and vampires are the fighters guild skills. Dawnbreaker, here I come!
Also, interesting that lycanthrophy is stamina-based and vampirism magicka-based.