but the room two rooms down is always occupied, for eternity. If you were to instruct everyone to pack their bags, exit in exactly 10 minutes and move two rooms up, you’re always going to have people being late and not vacating the room, so you’ll be dealing with people at reception complaining that they don’t have a room, or that there’s someone in their room. If you’re telling people (or indeed boulders) to move into occupied rooms anyway, then just tell sis & boulder to move into the first two rooms without moving anyone. If you’re not, then wait for someone to check out, as they’d have to wait for a nondeterminate length of time anyway.