I think this goes back to when we were kids and they didn't even heave seat belts in the car, and if they did you didn't use them. Not as safe as possible, but quite a few of us made it anyway.
We use the "airplane" method - sitting down, strap in. Gotta get up - get up and do what you need to do and come back and sit down. Sleeping in bed? Easy to rig up a belt for that if you want.
Sometimes we get so safety conscious we forget to live a little. All those wonderful options with a motorhome and you cannot use them when moving? Life is a risk so take a few, you already have of course and are still reading this so you made it!
Safest all around would be a five-point harness with HANS and helmet but that takes the fun out of it unless you are driving around Telladega, which I'd love to do sometime in the Phaeton!