We went last year, over 100 minutes before the show. We couldn't stand the crowds (and we're hardened Disneyphiles!), so we left. As we went through the entrance, cast members were closing the queue, 80 minutes before the show.
I don't care how good it is, nothing, and I mean nothing can be worth that sort of wait, in that sort of heat, with that number of people. IMHO
That said, we're going to try again next year! But I think we'll try and book a dinner + entrance deal.
Ian