How old is too old? A number of years ago the director of my Ph. D. research asked me, "How many more of those trips are you going to make?"

I answered, "One too many."

I was 71 last spring and the guys with me, ranging from 5- to 20-years younger than I, agreed I was the toughest guy on the trip. And we did a rugged bushwhack.

So my answer is, "it depends." Fitness, character of trip, quality of gear -- all of which have been discussed above.

As a footnote, sleeping on a Therma-rest, with wadded-up jackets for a pillow, I sleep great on the ground.

Tim