[@Lucius Cypher] My rule of thumb is to have fun. Something VERY OVERLOOKED recently. If I wanted to go and do OP shit and ruin RPs then I would do it without your permission. And not like even if I did people couldn't object and refuse to accept it as canon.

But for the sake of the RP, lets go DnD rules. Casting a basic level magic would take both actions a turn, so movement and action. This means 6 seconds according to 3.5 rules. I'd imagine every next level (El, Ur, Al) would effectively double the cast time, so an El would be 12 second, Ur 24, and Al a whopping 48. Granted he has the runes to do so.

Lets put rules on the runes too, so lets go. Simple spells are mostly caltrops or air runes (eg only needs the air around to cast). El, Ur, and Al woulf need actual runes. I am thinking wood/leather, stone and finally metal/crystal in the order of the spell difficulty. DnD rules would probably let him regenerate set amount of these per short rest, but how much I leave it to you. 

I think thats fair, and still wont make the character, well, useless. His whole character revolts around this attunement, and neutrality and taking it away would make him absolutely boring.