that is exactly what i do. although all my torrenting is in the evening and overnight.
i just recently dumped my comcast deal, so ive been tethering for little over a week now, im already over 17gb usage. thank god for the unlimited plan.
you see that gets their attention and I expect in the future AT&T will be cracking down on the abusers and excise use. 17gb and your time of usage is enough to flag for father investigation and they will find you in violation of your contract.