I bet a lot of those flyovers are the unplanned type.
With a few fighter pilots (and others) dropping by thier old haunts just for the heck of it. They gotta get their hours of stick time somehow, and why not fly by the acadamy for old times sake. ourright its probably not necessary that they do the fly by's, but it is probably just as valid a training exercise as most others (at least in some cases...)
The long & short of it: I bet they are just having some on-the-job fun.
Scott Evil