Complex sentence: FEMA would begin asking residents to vacate their trailers in March of 2007, but because so many people were unable to receive a trailer until a year after the storms, FEMA has already extended that deadline indefinitely.
Split into simpler sentences: FEMA would begin asking residents to vacate their trailers in March of 2007. But because so many people were unable to receive a trailer until a year after storm, FEMA has already extended that deadline indefinitely.