Regardless of whether the finger scan is erased or they are older tickets etc., you have ABSOLUTELY NO WAY of knowing what is really left on the tickets until you get to WDW. This means that you could potentially get there, having paid for your tickets, and find out there is nothing or less than what you thought you were paying for. Why add that stress to your holiday???
When you sit and figure it out, if you purchase a 5 day hopper, your price per day for what you are receiving is very reasonable, IMHO.
Good luck with whatever you decide.