Just hope somebody outbids you. Disney prices these tickets by taking into account an average number of days of usage. Some people may use it all, but they hedge their bets that most will not. As the tickets specifically state, they are not transferrable. They should have been required to sign it upon their first entry...though CMs don't always check to make sure there is a signature. Also, they are usually only good for a certain number of days from the date of first use (15 days?).
You won't be able to upgrade an expired pass. It's clearly unethical and fraudulent to attempt to use a pass which is non-transferrable.
It's nice to try to save a few bucks, but DLR really needs the money.