I used to have a schedule that allowed me to maintain a steady commitment of an hour in the morning and an hour in the evening. I did that pretty regularly (ever day) for a year or so. Then life intruded. You know, job, kid, business, the whole nine yards.
I didn't develop to the stage where I could reduce the hours of sleep to accommodate meditation time. Plus, I have to admit, sometimes I'm still afflicted with laziness. Lately there have been days when I don't formally sit at all, which is pretty shocking for me, because in my mind I'm seriously committed to practice.
In the approach that works best for me (Goenka), it's recommended to meditate for an hour in the morning, and hour in the evening, plus a short period before getting out of bed and before going to sleep, plus whenever you've got some extra time. When I found that I was unable to maintain this, I began asking an assistant teacher about it. In fact, I asked more than one, because I struggled with the issue for some time.
A got a couple of answers that I find useful. One assistant teacher encouraged me to meet these life circumstances with equanimity, recognizing that things are always changing. Another said that even a shorter period of meditation time can be effective.
One AT told me that the recommended length of time is intended to ensure that there are at least some moments of good concentration in there. He said that even just a few minutes of good concentration can suffice. (Not that that's an excuse to sit for shorter periods, of course.)
I have found that short periods of meditation can be very effective, but when I keep up a regular regimen of longer periods, it's much more beneficial. The balance, of course, is still finding time to fullfill my responsibilities to my family, employer, my clients, my friends, and myself. I can't just drop out (nor would I want to at this stage).
The question posed in this thread, "How many hours a week do you meditate?" strikes me in a very personal way, like a wake-up call. Thanks for asking.