It happened to me -- I was in the aisle seat and on a flight from PHL-LGW, and the woman on the window seat woke me up to use the can about 2 hours from landing---of course I could not fall back asleep, but she promptly nodded off and only awoke after we landed, at which point she made a big deal of saying how tired she was. I was really peeved, but I can only blame myself, because she used the bathroom immediately after takeoff, as well as two more times in the first two hours of flight. I should have switched with her then. So having been on the receiving end, I think if you are gracious, it really goes a long way.