I believe if you just enjoy just hanging out, doing the things that you like to do.. i.e. read book, watch movie, sleep like its part of your 8 hour sleep.. you'll get off the plan fresh and ready to go. Nowadays, flights seem really short when I doze off and wake up and its time to get off the plane.

I appreciate the rest after the rush of packing.. packing the kids.. going through check-in/security/boarding.. once on the plane, I sleep like a baby.