i think this has always been a dirty little secret folks haven't been realizing. If you stay on site, you will be hooked into the system when you make those ressies, even if you are using old tickets.
However, if you are staying off site, I don't think you'll be able to put in your tickets, and start holding FP+ for a date in the future. If that was allowed, I could get on today and save FP+ with my tickets I have days still on. I think it would just be too difficult to do. You'd have tons of fake FP+ ressies that would never be used. APs could do this bigtime also, if they aren't limited.
Let's say I plan a week vacation to WDW in October, and I have some ticket days left, would they only let me save FP+ for as many days as I have on the tickets? What if I say "I will buy tickets when I get there"? If they allowed you to get FP+, everyone would save them for every day they were in Orlando, and then choose which day or two to actually hit the park when they actually get there.
Sorta like the AP I recently bought at
Disneyland. I paid for it before I went, but I didn't have an AP NUMBER until I actually used the voucher (which did have a number, but not a meaningful one). Now, the DL hotel let me get the AP discount, but I had to show the AP at the front desk, once I had it.
There is no way FP+ will be given to people with nothing but vouchers for tickets from other sellers, or promises of tickets bought. You will have to physically HAVE the ticket in your hand.
Even if you are buying a Disney package. Let's say you say "I want length of stay tickets", and they are reserved for you. You could show up and say "well, money is a bit tight, so we are instead of having 8 day LOS tickets, we just want 3 day tickets". Will they let you keep the FP+ for three days of your choice, or will reseting that part of your ressie release those, and you then have to grab new ones again?
I really think this is meant to be a resort perk first, then a perk for those savvy enough to know about it. For Joe Sixpack showing up at the gate to buy the most expensive tickets for his family of four on their trip of a lifetime, he'll be screwed. Especially if the
D23 rumor of none being held back is true.
Jason