This is good news: "Lost" now has a definite end date:

ABC has agreed to let the producers of Lost set an expiration date for the series: three years in the future, Variety reported. The series will wrap after the production of 48 additional episodes that will be divided into three, shortened 16-episode seasons.

It sounds like the writers were starting to hear the criticism:

Cuse and Lindelof wanted an end date in order to mollify critics of the show who worried producers were simply spinning their wheels as they worked through the show's layer upon layer of mystery.