Sorry, I think Bush had something like 300 or 350 flight hours, which would come out to 12 and a half to 14 and a half days.
But then again, how many of Kerry's four months was he actually in Cambodia....
Since it takes almost an entire day of pre-flight briefing, flying 1-2 hours, post-flight briefing, then Bush spent much more time at his job than Kerry did on his little boat.