Most of the state rest areas that I have seen post a limit on the length of time you can park. That limit is frequently 4 hours and occasionally 6 or 8 hours. Any of those are long enough for a nap. And who is it that is keeping time, on you? :
That said, I do not use state rest areas for more than an hour of rest and or change of drivers. I made this decision many years ago, based upon personal experience. And, I have read the stories. The I-70 killer (serial killer) was one of the early ones. Don't know if they ever found him. Had a few personally unpleasant experiences that set me against staying in one of those for any length of time, and never at night. I look for a population of cars and trucks there, and then stop for a short period if there are enough people there.
Stopped, once, near Twin Falls, in a car. Wife got out to go to the restroom. I saw a man watching her, so watched him.
Sure enough, shortly later, he folllowed her. I got out, at once, (properly dressed for the occasion,) and followed him, moving as fast as I can move.
He wasn't in there for more than seconds when he came running out with a terrified look - ran to his car - got in and moved on. I tried to get the plate, but wasn't fast enough.
She came out, shorty, and asked me, laughing, "Did you see his face?"
;D
You see, she had been "properly dressed for the occasion," also! Several times on the way home, she would burst out laughing, again. She didn't much like rest stops, after that! :
Don't know why! She sure was "entertained" that time!
:
Ray D