I've read lots of Lost threads since the finale, and many of folks, including Jimmy Kimmel, seem confused as to what happened. The way I look at it, the flash-sideways universe, aka "purgatory", is just like the Nexus in Star Trek: Generations. For every new arrival, it always seems as though you just got there, but once you figure out where the heck you are, you have some sense of the "passage of time" as you bring everyone else up to speed, like when Picard convinced Kirk to stop trying to get Antonia to marry him and to stop worrying about cooking those goddamned Ktarian eggs. The difference in the Nexus and Losturgatory is that the Nexus is heaven, and the Losturgatory is heaven's waiting room. 
