My dojo (NOT USAF- though it used to be) counts hours, but if you train 2 hours, you mark down 2 hours towards your test instead of just one. I believe several dojo's do the 1 hour/day thing no matter how much you train though. Even though people can be in the same organization, interpretation from one sensei to another creates a unique dojo environment..... thus the differences in how testing is handled.
In my dojo, we are lucky if testing is held once a year. It just doesn't happen that often, which is fine for me since I hate testing.
It usually seems like he waits until a few people are ready to test for that rank and then it happens. Our last test was held last November for four people taking 5th kyu tests.
it's the same way in our org. There are hours requirements for rank, but it's a very loose system of measure and one that is easily overridden by someones ability. Despite the hours requirements most dojo's only hold testing once per year at best. Dan testing is only done at summer camp, no exceptions.