Sorry for this non-answer, but I really think it depends a lot on how one normally functions. I sleep on any TATL flight as much as I can, while my husband rarely sleeps more than an hour or so. I couldn't survive with as little sleep as he gets while traveling, nor could he force himself (without some heavy doses of medication) to sleep as much as I do. If you can function on a short night's sleep, take the Mayo Clinic's advice, but if you routinely need more rest than most, listen to WebMD.