Events slow to load even with ajax enabled

I have a lot of events on my calendar and ajax certainly improves the speed but I still find it a bit slow. When a month loads it seems like half the events load then there is about a 2-3 second gap before the rest load.

Not sure if it's relevant but it always seem to be the bottom half that loads first, and I have noticed that the beautytips flyout I have only shows on the events that loaded first.