Rendering is pretty much limited by the GPU hardware. Events depend on precisely which events you use. A single event to loop a million times a frame would drag the framerate down, but 1000 simple events would still be nice and fast.
@AmpedRobot to give you some indication, apparently Super Ubie Land has 3500 events and it still runs very smoothly. As Ashley said, it's not he number of events that matter - just the way they are implemented.