For so many reasons, this clip from Dr. Strangelove comes to mind when this topic is discussed.
Greg Garrett hits the nail on the head. And while rapture enthusiasts are easy targets, we are all pretty adept at finding excuses to put aside the Kingdom we're supposed to be laboring for.
That said, please don't feel bad about watching Slim Pickens ride a nuclear warhead to the ground. That's never a waste of time.