Well, the season is officially over on FOX, so I presume that the Season 18 episodes have been sent to the syndication market by now. It does seem a little earlier than usual, though - traditionally, the most recent network season doesn't enter syndication until August or September.
But on the plus side, maybe this season's quick entry into the local stations means that they didn't have to cut as much out of these episodes. They keep whining on the DVD commentaries that the show length has been cut down to 20 minutes (and yet, Al Jean still can't get the show to come in at the right length to save his life), so maybe that's suitable for the syndicators' needs. Just substitute most of those friggin' two-minute couch gags, and a lot of Season 18 would easily meet the standard syndication length.