I think that 48 hours notice required for a hotel room reservation is fair in order to avoid charges.

In some areas that are extremely busy, 24 hours notice may be enough time to reasonably allow someone else to rent the room, but in areas where reservations don't fill that fast, 48 hours is likely more appropriate for business.

I've have never waited less than 24 hours before knowing when and where I wanted to reserve a hotel room.