That’s a tough question to answer. It depends on the freight train traffic at the time, as it’s a shared line with CSX, mechanical failures, etc.
We just took a trip to WDW March 3 and March 11. The trip down was pretty much on time, but the trip back was delayed three hours due to the fact the train we were boarding was three hours late getting in due to engine trouble.
So... you never know.
Expect the best, but prepare for the worse.