I know there are "birth-month audits" that occur yaerly on your birth month. But that is to get your paperwork up to date. Physicals are only required every 5 years, and I have been in for 9 1/2 years, so my next one is coming up and I don't really remember when my first one was.
But I do know that I read an interview with someone from Bush's unit who said that it was a regular occurance for a pilot to miss his physical due to civilian obligations. And that a make-up exam could be tricky to get, because the medical staff was mostly week-end-warriors as well, and they wouldn't automatically open up shop to suit one person.