Question:
Just wondering how long you are allowed to stay at a rest stop? I know highway patrol will chase off 4 wheelers after few hours, just wondering if that goes for 18wheelers to.

Answer:
Are you talking about Truck stops like TA, Pilot, Flying J, Petro, Loves, etc, Or rest areas? Like a few parking stalls, a restroom, a water fountain, a vending machine, lots of drug activity, and lot lizards? I hope I can park and sleep at either one I have yet to be run off my a DOT officer for sleeping in a rest area overnight. I mean I'm sure if you spend a couple of weeks making it your home (I can't imagine why) then I am sure they will say something. Also where else are you suppose to sleep at? We don't get to spend the night in hotels and globetrot like Chad
Although I have heard of a guy that had a heart attack in his sleep while sleeping at a truckstop (in his truck) after a couple of days from not hearing from him his family started to worry and called the police, well needless to say a week later they found him at a Petro, so he spent a week at a Petro and no one said a thing or checked on him. So I think you will be alright.
Answer:
I've had police come up to the truck while I am in a rest area, but all they were doing is checking on me to ensure that everything was okay. I have never had any problems with them telling me to move on down the road. They will look a little bit more closely at cars, but if they can see that someone is clearly sleeping in a car, they rarely bother them.

Answer:

Depends on where you are.
Some states have time limits, and you will get chased out if a cop sees you there for too long. Other states don't care.
Answer:
The states that do patrol the rest areas generally tend to be more concerned about the guys who park their trucks on the ramps. They are an easier target.

Answer:
States that limit your time in a rest area usually post a sign giving that limit.
Likewise, ramps are usually posted "No Parking" or "Parking not allowed beyond this point".
Contrary to what the BBR's and truckstop lawyers tell you, you have absolutely no right to stay beyond the posted limits, out of hours or no.
The state is not required to allow you free, unlimited, parking.
If you're told to move and you claim you're out of hours most will be happy to arrange a tow at your expense.