I was wondering if signing up for this benefit is worthwhile. It appears that some timeshares are offering this as an option for doing an upgrade. After paying an enrollment fee, you deposit a week that you don't wish to use, and they in turn will rent it out. You then receive double the maintenance fee. However, the timeshare specifies in the contract that they have nothing to do with PTC and will not be held liable if it doesn't work out although you are required to pay a membership fee upfront (this fee is separate from the enrollment fee paid to PTC). It seems that many people are signing up for this.
http://www.privatetravelcorporation.com/#!solutions/ch6q
http://www.privatetravelcorporation.com/#!solutions/ch6q