I'm surprised that no one has stated this yet, but why would you do that unless you were absolutely, positively, beyond the shadow of a doubt, never going back to WDW for the rest of your life. Save those tickets for your next trip to WDW! They NEVER expire. DL tickets are generally cheaper, so you would essentially be losing money using WDW tickets at DL.
example.... for the sake of argument let's say you paid $20 per day for these older tickets and there are two days left on them... for a total of $40.
But WDW daily prices are now $50 (just for the sake of argument... I know it is not this price) and DL prices are $30. You are using a $20 ticket to pay for a $30 day in DL rather than a $50 day in WDW. Again, I was just using random numbers for an example... but I think you get my point.
The only reason I could see to use these would be....#1. you just cannot possibly come up with the cash to go to DL right now any other way. or #2. you are a person who easily loses/misplaces things and you figure you have been lucky to hold on to these for this long and figure you better use them now. or #3. Like I stated above, you absolutely will never return to WDW for as long as you live. HTH.................P