My wife sleeps all the time,but its usually on the interstate. When we hit a good bump at 80 and her helmet clangs off mine , she'll be up for a while because its hard for her to sleep with me cussin LOL
i hate to put a damper on this and i know people do this. but its dangerous. ON t.v. show alaska state troopers, they had a segment about a biker and his woman who fell asleep , make a long story short, he tried go around a truck, a quick motion to left, then sees oncoming truck quick motion back into lane, as he did this, her head whip lashed back into oncoming 18 wheeler. she lost her head hitting the oncoming truck.
Happens a lot actually, not with me, but on long rides on touring bike co-riders fall asleep all the time. Not necessarily right, but it happens...one of the reasons why it is a good idea to have arm rests or seating with "wings" or similar protrusions to help them stay in place.:s