Usually by the time of the reservation, it is well past the banking deadline for most of my contracts, so I haven't had this problem yet, but I have had to reschedule a few times for people who had something come up and couldn't make their first reservation. But I don't rent a lot of points out, just my extra ones, which leads to a lot of studio weekend reservations.
Overall, renting isn't to bad an experience as an owner, but it takes a lot of patience because most people who inquire on the "Rental Board" don't know how
DVC really works. So you spend a lot of time explaining how the points work and their limitations. It will usually take 10 to 20 inquiries before I actually get someone to commit to a reservation, so you spend a lot of time checking availability on the RAT before you lock someone down.