Well BT have a "recommended" limit of either 40 or 50gb a month. In July I downloaded 50 and they emailed me (well, my dad) saying if I did it again they'd charge £1 per gb over the limit. August I ended up downloading 80gb as my new laptop crashed just as I'd finished downloading all three of Veronica Mars season 2, Battlestar Galactica season 1, and Farscape season 3, and so had to do all of them again, thus doubling my downloads. They're now saying the limit is 40 a month, but I swear last time it was 50....
Anyway, now I'm pretty much caught up with the four shows I watch that are still going, which are Lost, House, Veronica Mars and Battlestar Galactica, so from now on I'll on be downloading a few episodes a month as they're released, so I may have some gbs spare for downloading SG1, if I so desire. But still... that's a decades worth of episodes to watch, it may take some time.