Listing your time share for rent

I have listed my unit at Bluewater Resort and Marina on Hilton Head as have several other people. In watching all of the postings I have noticed that most of them don't get rented. Do you think it's because of the location on the island or because, even though it is considered to be a premiere resort, it just isn't well known enough yet? How long should I keep it listed before I explore other options? Thanks for any advice.