As the PP said, DLR now enforces return times for FPs. They, like WDW, used to allow people to return anytime during the day after the window opened, but soon after WDW started enforcing return times, DLR began to as well. It is worth noting that DLR does not have a grace period time printed on the FP (WDW used to before they went to FP+), so whether a CM will honor a late FP (and by late, I mean something like 5 minutes) varies by CM.