I own 7,000 WorldMark credits which I use almost exclusively to trade through II. My experience is that WM trades well for shoulder/off season in higher level/higher demand resorts e.g. Marriott, Westin, Hyatt, HVGC-when available. I have not had tremendous success in high season for the higher tier resorts but I found I can simply rent those weeks if I want them through Redweek, VRBO, etc . Others experience may be different as I usually try for very difficult high season trades e.g. coast of western Florida in late February/March with a "Request First" trade in II. That said, I have greatly enjoyed the trades I have made through II in shoulder/off season and have zero complaints. On rented credits, I have actually not ever had to rent credits but I am quite sure that as long as the rented credits have been deposited in your WM account before the trade takes place it makes no difference whether the credits are rented or part of your annual allotment of WM credits (although you will need also need a housekeeping token for the II trade which cannot be rented but can be purchased from WM if you do not have any housekeeping credits in your WM account at the time of the trade). You should be aware that WM limits the number of credits you can rent, I think the limit is the annual allotment of WM credits, that is, you cannot rent more than the number of credits you receive annually but that limitation amount is subject to check since I have never rented credits. Even if the credits are not in your account at the time of the trade you can purchase"Fax credits" from WM to complete the trade, although there are amount and time limitations on purchase of Fax credits which I do not recall the specifics of ( I have never had to use Fax credits and do not know precisely how that would work on a "Request First" trade in II ) .