But go by so much quicker than watching a single episode of the Seven series.
You can easily get through a week in a night, certainly pre-FNL era anyway. 20-22 minutes for a daily show, 46 minutes for evictions/nominations in the days when hour long shows generally lasted an hour.
At a rough guess a week of BB on Ten clocks in at just over three and a half hours, which is not much different to a week of three episodes on Seven. For later series FNL and the increasing number of specials adds to that a bit, but you'd still fly through it quicker than you think. Also don't think watching FNL would be crucial in rewatching the series - you only need to know who wins which you find out in the Sunday show anyway.