We usually arrive before check in and we usually stay until 3 on check out day at BWPPI. I have always thought it was a perk that I didn't have to pay anything extra to park there after I had already checked out. Many places will charge you a full days parking to stay after check out, if they allow you to stay at all.
We have always been able to stay until midnight the day of check-out at HoJo and Ramada Maingate (both without having to pay for parking) - that's why I was surprised I couldn't stay there, too.