I think you will find that most of the veteran members of TUG have bought and sold multiple weeks, many of them on the resale market.
You really have to determine the price you can get now versus what you paid for the week. If the week was purchased directly from the developer, expect the current selling price to be pennies on the dollar, unless it is a Marriott, Hilton, Disney, or similar top drawer product.
I own one week that would be worthless if I tried to sell it--probably wouldn't even fetch a dollar on Ebay. I acquired it for free about 12 years ago. I would never take it now as I have learned enough to know that free isn't free--there are maintenance fees, Special Assessments, exchange club fees, etc... Through years of good advice on TUG, and lots of trial and error, I've learned how to obtain great trades with it, even to the Manhattan Club and Hawaii. As the saying goes, "When life gives you lemons (or you are so ill-informed you ask for one), then learn how to make lemonade"