Unused FL resident ticket

For those of you familiar with FL resident, Discover Disney tickets, I have a question. We (non-FL residents) are heading to WDW in early May. My sister and her husband live in FL and are hoping to join us for part of trip. In the event they are not able to join us, do you know if they’d be able to get a credit for the price of their tickets to use at a later date? Does anyone know how said credit would work - would they only be able to use it for future tickets or could it be used towards a future room or some other Disney purchase? Furthermore, if they both need to bow out, would each end up with a credit that only they could use - ie would my borther-in-law end up with a credit that only he could use? It’s much harder to my BIL to get away, things often come up at work rather last minute that prevent him from getting away. Thus, a credit that only he could use (vs my sister) is not ideal. But having him wait to buy a ticket until he actually arrives at Disney prohibits him from FPP rides with us… any work arounds that I’m not aware of? I was hoping that if they simply ended up with a credit for any unused ticket (that could be used by either of them, and thus my sister could use later since she is more able to get away), that it would eliminate some of the stress of committing… it’s not going to help with the stress/fear in the days leading up to the trip that something will come up that will require him to stay.

TIA

As long as the ticket hasn’t been used, generally you can apply the purchase price of the ticket toward a ticket later. So, let’s say your BIL bought the ticket now for $150. But, he can’t go. So, 2 years from now, he finally goes. The same ticket is now $180. So, he should be able to pay the extra $30 as long as he has the original unused ticket.

My understanding is that any discount he may have bought the ticket at still applies. So, really the difference you pay is not in the price you paid versus current price, but the face-value of the ticket when you bought it (regardless of the price paid) versus face-value now.

So, if a ticket is worth $175, but he bought it for $150, then later, if the new ticket is worth $200, he would only pay $25 to upgrade, not $50 even though he originally only paid $150.

Hope that makes sense.