The more I think about it, the more I think that the concept of the Last Dispensation was one of Joseph Smith's cleverer ideas.
I realize that it wasn't a complete invention, considering plenty of other Christian denominations believe that the end of times is quickly approaching. But I've rarely seen people outside of Mormondom take that belief so dearly to heart.
The sense of constant vigilance is pervasive in Mormonism. The belief is that the Second Coming of Christ could be at any time and that all the signs are piling up. This gives members the feeling that they're running out of time to achieve their potential. If you haven't repented of your sins and magnified your calling and done your family history by the time Jesus comes, then you've kind of missed the ultimate deadline. You don't want to be the guy that has to say, "Oops, sorry, bro, I was a little behind schedule and I'm not ready." This is why church leaders repeatedly urge us to be prepared.
The real reason we're supposed to be prepared is that when you're in a continuous state of heightened panic for the fate of your immortal soul, you're not taking the time to stop and think about what it is you're doing. Rushed decisions are often bad decisions, and the more the church cracks the whip of a looming apocalypse, the more rushed the members feel. Being part of a perceived last-second full-court press makes people focus on doing instead of on what is being done--and instead of why what is being done is supposedly necessary.
If you run into a building and start screaming that there's a fire and people need to evacuate, a lot of people will start evacuating. In a suddenly high-pressure situation, who's going to wait around to see if you're right? Who's going to question you about how the fire started to see if you're making it all up? The thing you're screaming about is dangerous and you're really selling it, so for their safety, people are going to take your word for it. The big difference though, is that if you evacuate the building because you trusted the guy shouting fire, you've wasted an afternoon...but if you strive for Mormon perfection because you trusted the church, you've wasted an entire lifetime.