The only way to tell if you have days left on your tickets is to bring them to WDW. The guest services desk outside any of the theme parks will be able to scan your tickets and tell you if you have valid days left on them. The front desk of your resort may be able to help you also. My family is about to use up the last of our non-expire waterpark tickets purchased in 2004.
They've been a great asset for us. I hope you have days left too!