It partly depends how many tables you're playing...your return in BB/hour should be more if you're playing three tables as opposed to 1. Doing triple tables in OHL I've had some 2-3 session hot streaks where my BB/hour has been in the 20-25 range. Sadly, bonch is right, its non-sustainable, but its awfully nice while it lasts and even nicer if your losing streaks don't negate it
