I don't think there's any rhyme or reason to the turnouts. I just do what I feel comfortable and safe doing...paved or unpaved, signed or unsigned. Don't drive yourself crazy thinking too much about the people behind you. They'll get over it...even if they have to shout at you or give you the finger. I take comfort in knowing that I am driving safely.
With rest stops few and far between, I just try to find Walmarts, truck stops, etc. with big parking lots that are right beside the freeway. I usually do this online (Google maps) the night before the drive.
