The first road trip we took with our Tesla Model S was from the SF Bay Area to Lompoc, CA, to see a SpaceX launch. (Seeing ANY rocket launch in person is a highly encouraged activity by the way!). The timing of it allowed us to drive there, see the launch, and drive back the same day, but getting home pretty late.
Getting into the bay area, it was dark, and I was damn tired. Had this been a long trip of some kind, I'd have at least pulled over and done a power nap, but I foolishly decided to press on, since we were less than 30 minutes from home and bed.
I'd been using autopilot for most of the trip, closely supervising it of course.
Suddenly I was awakened by the frantic, loud beeping that you get when you don't keep some minor torque on the steering wheel for a while.
It scared the hell out of me and my family in the car.
With their help, we were able to make it home safely.
Your specific use case is valid, but the other commenters are also correct. Autopilot still needs to be supervised, and one should NOT be driving while extremely drowsy.
In my many decades of driving, and countless long trips, this is the first time I've fallen asleep, and I've always done the right thing and (at a minimum) taken power naps as needed.
But circumstances conspired and I did the wrong thing.
I'm not claiming that Autopilot saved our lives or anything; I would almost certainly have been woken up by the rumble strips when the car drifted out of the lane.
To those who might argue that using Tesla Autopilot might tend to cause people to take bigger relevant risks: that's possible, but it's been a godsend for us. Using it doesn't make me, personally, any less attentive of a driver. Indeed, I'm quite a bit more alert to the important things than without it.