Back on topic, a local retail park has a "No return within 3 (or similar - I forget the detail!) hours" rule for parking. Not quite sure what they're trying to achieve, but it makes it difficult to drop someone off to pick up later, or nip back 'cos you've forgotten something or the thing you bought is faulty, without the risk of having to fend off attempts to levy a (probably unenforceable) penalty.
I think the idea is to allow for the parking enforcement, who cannot be there full time, a reasonable time to come round between visits. Otherwise someone could say they had left and returned after 5 minutes.