I was hitting 200-350 GB a month on my 10 Mbps connection a few months ago (before I bought a NowTV streaming box). When I rejoin NowTV (either with films or entertainment) my usage may go up. I want to go for fibre but see no point paying for PN's unlimited "up to 76 Mbps" when my line is estimated at around 33.5 Mbps, so may get a line from someone else.
One thing I suggested some years ago was for PN, as part of their billing cycle, before they zero the usage figures for each day (as displayed on the 'Usage this month') to e-mail the figures to the customer and then zero them. At the time, I think I had a 60 GB limit, or it might have been different, but it was at a time when a user had no independent stats historically if they were charged for higher levels of use, so it would have been primarily of benefit before 'unlimited' came along, but for anyone curious as to their usage over a number of months it would also now be quite handy, and probably a tiny overhead for PN in terms of processing.
If you run a business, have a second ISP and backup web hosting...