Pete,
I have some numbers for you based on Google Earth Measurements:
- 1 tee to 10 tee, with all the walks in between - 2.59 miles
- 10 tee to 18 green, with all the walks and bridge detours - 2.62 miles.
- Walk to the range from main building and then to 1st tee area: just under 1/2 mile
The course numbers also assume every shot is down the middle and no missed greens. So when you add all those up and include an extra bit for hitting wayward drives and approaches, each round is easily going to be minimum 6 - 6.5 miles. So in that context the Masters is basically a marathon over 4 days.
But I'd bet its pretty close to that, or even more, for every tour event.