matterhorn usually goes down twice a year, between new years and summer, and then between summer and christmas. sometimes it only goes down once a year, but that one is generally twice.
They try to have things running for thanksgiving, but that's not always possible. Last year they did major rehab on the track (I think it's mostly new track) so it was down more than usual.
Also last year Fantasmic took a nine month hiatus. I think it was mostly economic, but I haven't seen it since it's been back up so don't know if anythings changed. They're currently doing it nightly, but usually in off season it's weekends only. ( and sometimes Sats only) Like I said last year though it was down from after summer to this summer, so there's no quarentees.
Usually the best times for little to no rehabs is Summer and between christmas and new year. This year however there are more that are down during that summer than normal