I see a lot of these posts asking about the policies of the big chain stores, but the reality is that the local municipality rules trump whatever the company policy is (if they even have one). My local Wal*Mart has signs all over the lot that say "NO OVERNIGHT PARKING". But due to it's convenient location just off of Rt. 80 a lot of truckers and RVers park overnight. Cops usually look the other way, but over the years they have to clean up when the lot-lizard activity gets out of hand. I've parked there overnight without issue. I've also parked behind our local Home Depot without issue. You just need to lay low.