A lot of people discussing the 1 hour in the morning, 1 hour before bed requirement. I also found this impractical, but lately I have been pondering something that Goenka said on this subject: If you don't have enough time, sleep less. When I heard this, it sounded ridiculous, since sleep is so important for the body.
A theory I have been developing is that perhaps meditation that achieves a no-mind state for a long period of time, may allow the practitioner's brain and body to enter the same kind of restorative repair cycle that it normally only enters during unconscious sleep (the only time a normal person's mind is truly shut-off).
A variety of experiences have lead me to suspect this, most profoundly being the night AFTER my 10 day retreat ended, when I was quite tired from a long day, having stayed up past midnight, despite having gotten up at 4:30 am that day for the final day of the retreat.
When I lay down to sleep, exhausted, I fell into a deep meditative state. I got up and opened my eyes, took a walk around the block, went back to try and sleep, and immediately was back in a meditative state. Gave up and just went along with experiencing being in that state all night, since I was totally aware, yet in the morning felt very rested despite having not slept a wink.