Consecutive, and then there's a waiting period (7 days) before you can do it again. But, you MUST have the permission of your roommate before you can have overnight guests, especially if you plan to do it on a regular basis. Not everyone is comfortable with that, and if they're not, then you either have to come to some sort of compromise or simply respect thier views.
You can find the actual Guest/Escort policy right here:
http://housing.mcmaster.ca/Residence...ts/Guest-1.pdf
Oh, and as Nicole mentioned, on Thursday/Friday/Saturday nights, most residences have staff on duty in the lobby to sign in guests, and each resident is allowed a maximum of two. Outside of these times, they do not have to be signed in.