We have had luck around 10 and 11. Typically if they do one, they seem to do more than one. We tend to go the park at rope drop, get a few rides on EE, FP the safari, then head to Rafiki's. supposedly you can ask a CM in the park in the morning to check the schedule, but we haven't ever tried that. Note that Rafiki's may open an hour after park open. This is why our touring plan has worked well, as we seem to get to Rafiki's shortly after they open.