C. Osbourne wrote:

I'm going on some long flights soon, and would
really like to do some sleeping during the flights.

Try climbing to altitude and couple the GPS with the autopilot. If you
have a way of setting the cabin pressure at about 9000, do that. It's
easier to sleep up there.

Then turn down the COM1 volume a bit, and tune COM2 to 121.50 and turn
it up loud. If ATC really needs to get to you, they'll try on 121.50,
and that should wake you up.

If you're flying single pilot-in-command, make sure your passengers
fall asleep before you do, and make sure you're wearing sunglasses that
wrap around so they can't see that your eyes are closed, just in case.