It's probably my post that you read about it shutting down in early fall and not opening again until early June.
This is largely based on my experience when I had a So. Calif. annual pass which has the holiday periods like Christmas and Easter blacked out as well as all Saturdays. I just checked the DL website and they have it scheduled to resume starting 12/17, just in time for the Christmas holidays. So, in other words, Opps, I was wrong! What I do know is that it doesn't run everyday during the off season because the park closes early during the week then. It is scheduled to run everyday during the Christmas Holidays though.
Do keep in mind, the sailing ship Columbia is down for refurbishment. If they should find it needs unexpected repairs which would delay the Columbia from sailing, then Fantasmic will also be delayed because it plays a pretty important role in the show. Hopefully someone else will be able to confirm this since I've been wrong before.