Sometimes I have teams that think there is little point to being ahead of schedule. I try to convince them that things will inevitably come up that will take up precious time to sort out, so we need to hustle, as described in The Mythical Man Month. They understand the need to finish on time, but not the necessity to work harder than necessary to do so even if something goes wrong.
How should I convince them that hustle is important? Should I yield to their stubbornness and let things proceed on schedule, but not ahead of it? Is it okay for a manager to allow their project to progress such that they would not have enough time to deal with any minor catastrophe and still finish on schedule?
(Feel free to give software-specific answers, but I'm looking for as generic an answer as possible as this isn't a software team.)