This is just a theory but I have heard from many people that GWB had more than 375 hours flying F 102's!
Rush (I think it was he) said yesterday that President Bush did 6 months worth of flying in 5.5 months.
Also, there's a thread somewhere on FR that states the reason for payroll gaps is because the President served without pay. (you probably saw this already, but I think it's worth repeating)