I had a co-worker who once told me he had intercourse with his wife, and she didn't wake up during the act. She couldn't figure why she was so wet when she did wake up !
Well, I'm not sure I'd be necessarily be bragging about that, I'm no John Holmes, but I'm pretty damn sure if I got freaky with my wife while she was asleep, lube or no lube, she would surely wake up, and more likely than not, be very upset about the circumstance.
My opinion, it is an invasion of her person to attempt sex without her being conscious, either because she is sleeping or knocked out in some way. I even feel guilty masturbating when she is sleeping, not that it happens often, but has at times.
Now waking up to a blowjob is o e of my greatest fantasies, so that's probably a double standard. Of course, if I okayed the scenario, either for her or my pleasuring in advance, that would be a different thing entirely. But you HAVE to respect your partner, in every way. I can't imagine how creepy it would feel, as a woman, to have been violated when you were sleeping. A lot of women have nightmares from just that kind of situation.