This is why it pays to call ahead and ask the manager. If we have any doubt, one of us will call and ask. The call usually starts with - we would like to stop at your store, do some shopping, then have dinner but remain until morning when we will be on our way.
The response is typically positive. At one such place, we were told that there was a new ordinance against it, but the local police had no interest in enforcing it and the store had a policy that was the same. She just instructed us as to where she would like us to park.
Matt