Spending a night (or two) in a motel parking lot?

We'll be traveling (in our B) to an event at the end of this month -- and my brother and his wife will be with us. They have reservations for two nights at an Econo Lodge, where we originally planned to book a room also.

Now hubby's on furlough and we're trying to curb expenses -- which has me wondering about sleeping in the B instead of booking a room. After all, it's already there, right? We'd have everything we need and it would save us a tidy sum.

My brother and SIL would still sleep in the motel -- and since we're riding together, if needed, our license plate could go on the parking permit. It's in a decent part of town, so I'm not overly concerned about safety.

Has anyone slept in their RV in a hotel/motel parking lot before? Anyone do it frequently? I'd love to hear your thoughts and experiences. THANKS!