I've used my tethered Boost Mobile connection to briefly engage in bursts of tethered usage, spiking way over 5GB when I do, however I don't do it very often, maybe only once every 2-3 months.
I'm guessing that as long as I keep my excessive periods of data transfers to bursts (and not fulltime heavy usage), I'm ok. This if course is no guarantee of what you will experience.
Good luck, and don't forget the Thanks button.
