Me! Me! Me!
That's all I see when I read this thread. Entitlement.
We're all fortunate to be able to afford Disney vacations. Then, they offer a FREE system where you can get a ticket to cut in line, but no, that's not enough.
We turn the "privilege" into an "entitlement" and insist that we should also be able to come back at OUR convenience, and not when the extremely sophisticated computer system tells us to. The 1-hour time period allowing us to cut in line just isn't enough. And then when we get in the FP line, we get upset when they let too many Standby guests though at once.
Until several years into FP's history, I had no idea you could even come back "late". We only found out by accident. After that, we still tried to come back within the time printed on the ticket, but knew we had a grace period.
I'm all for them enforcing the return time, simply because I know how much R&D went into the initial system. The return times are calculated based on the number of people obtaining FP's, with the intent of evenly distributing the number of guests entering the FP queue at any given time. And in reality, the original system, if allowed to function properly, would have helped maintain a steady flow of Standby vs FP guests in the merge point of each queue.
Their "grace periods" seem needless. Why the 5-min early allowance? And why 15 minutes late? Why not just make the return time 1:20 long instead of an hour? Or, even better, make it 90-min, which would counter the arguments of ADRs running late or parades blocking access. If you can't figure out how to get to a ride in an hour and a half, perhaps this "complicated" system isn't for you.
At the same time, CM's can always use their Guest Service training to waive the return time for legitimate reasons. For example, if it's 7:00pm and someone comes up with a FP that ended at 6:30pm and claims they were stuck at [restaurant] for an extra half hour, sure, let them in. But if someone comes up at 9:00pm with a 7:00pm FP.....sorry, you're just bad at time management.
I know it's terrible to suggest that anyone follow a rule, especially at WDW. I mean, nobody has to abide by the "no flash photography" rule, so why should they have to come back to a ride during the time they agreed to when walking up to the FP machine?