You need to use the GAD ticket on the day you redeem it. You can't convert it to an unused ticket to save for another trip. You could upgrade to whatever ticket you will need for the next trip and add the no-expiration option (using the first day when you redeem, so you would need to upgrade to one more day than you need the next time), but that is probably not cost effective. You also wouldn't be able to upgrade it during your next trip if your plans change since MYW tickets have to be upgraded within 14 days of first use (your ticket would already have one day used when you upgraded it).
You can save your package tickets for another trip, though. They can be taken off your KTTW card or you can just save the card. If you are not within 45 days of check-in, you can downgrade everyone to two-day tickets without a fee, then upgrade individually once you arrive if anyone needs a different ticket. You can upgrade the GAD voucher to whatever you need for this trip and have two-day package tickets that you can upgrade for the next trip.
The package tickets won't expire until after you use them the first time, but the GAD ticket has to be used on the date issued.
