I find open 24 hours in CNJ rare if at all unless they are in stand alone private building where someone coming and going at all hours of the night would not be suspicious.
I do know a place in North Jersey that the girls live at the spa for weeks or even months at a time. It's not open 24 hours, but if you have one of the girls numbers, and you text her or make plans to see her late night after hours, you can park around back and they will see you. I'm sure there are probably many other places that will do the same.