Sean - It never hurts to ask. We've been in situations where signs have said no overnight parking but the manager has said its okay as long as we move on in the AM. Its also helps to build a "repoire" with the management (as RVers) whether you plan on staying or not. As soon as you meet them and they know your prerogative they typically leave you alone. 9 times out of 10 if someone doesn't ask it sort of implies a lack of respect...and I'm pretty sure the ones that are "camping" in the parking lot with a grill and lawn chairs and staying for a few days are the ones not asking.
I agree about the grill, and I think people's experience with asking generally ends up being pleasant but I think that's from the RV's perspective.
You stay one night... so do 4 others...maybe more, but the manager is there *every day*.
I can tell you that if I were a manager of something like a Walmart...even if I were cool and overlooking city ordinance... that 5 or more times a day getting pulled aside by a stranger and being asked if they could park in the corner of the lot would become very tedious.
I think they are either going to let you, or you're going to be approached by security.
My own take is that I would not find it disrespectful if an RV'er didn't interrupt my job so that I might focus on his world for an answer that I've already decided in advance and given dozens of times that month.
As a former bar owner I suppose it's not much different. I got asked the same questions every night, and eventually delegated the answers to my security staff. "I'm drunk...can I sleep it off in my car for awhile?". The answer was yes, but not only was I tired of being asked, it also involved me in giving permission to do something that was against city ordinance. The morality of it forced me to allow it, but I'd really rather not know... or pretend not to know.