On weekdays, I try to revise from 5pm to about 7/8 ish, take a break/play an instrument until nearly 10, then carry on until 11. So that's about 3 to 4 hours a day (which would be good but I procrastinate during those times a bit too much, still get everything I'm planning to get done though). Weekends is basically constant revision from when I wake up to when I sleep, with breaks for food and just general slacking off.
The most I've ever revised is during Christmas break. Pretty much constant past papers and worksheets from morning until night every day, for my maths igcse. Then I burned out for about a month, so I would recommend NOT doing that.