hmmm
just do as much as you can/want, but from time to time make just slow solves, I just started a week of just doing slow solves and hope for some improvement.
I guess I am solving cubes for about 2-5 hours a day mostly at night when getting bored but not tired. But most of the time is spred over the day, like 5 minutes here and 10 minutes there, then another 7x7 solve just for fun (it smiled to me again) so I would also say most of you cube a lot more than they think, just because of those little "pick up cube, scramble solve scramble solve, put down cube" things that add up to a lot of time...