I will admit that I have never backpacked without some degree of pain before the day is done. Last year on Roper's High Route I had over 30 days of walking to figure this out. Regardless of the weight of my pack, it was the pack on my body that hurt first - mild saddle-sore hips and shoulders. This has always been the case, regardless of brand of pack. This kicked in after about 2 hours. After about 4 hours my Morton's Neuroma started - burning pain in my toe. In general, my entire feet are my number two pain source. On long downhill sections, the old knees started hurting after a few hours. At the end of the day my knees mildly hurt no matter what. The last thing to give out on me, even on days when I gained 6,000 feet elevation, was my breath or energy levels. Must mean my old bones and joints are in worse shape than my old lungs! I would be interested to hear of other's gradual "deterioration" on the trail! My average day's travel was about 6-8 hours, 7-8 miles and 2,000-3,000 feet gain on off-trail terrain at average elevation of 11,000 feet.