During the busy seasons the lines do get longer. A couple of weeks ago, the week before Easter weekend, I watched the lines grow and there were no busses coming in. I hung around for about 30 minutes and finally two came in and they were loaded immediately. It was around 1130 hours and that is a heavy arrival time at MCO. I watched and only three other busses came in after the other two. The waiting depends on the busses getting into the airport. That morning the average time to the resorts probably went up about 30 minutes.
There are times when you are going to wait around because the busses may be loading at Disney and coming into the airport. When those loads are heavy everything slows down a little. If you do wait I think it may be entirely because the transportation can't get in there fast enough.