Males loose a significant part of their ability to produce cartiledge at about 36-40. At that time any scar tissue you have built up, bone chips, rim abrasion, etc, is no longer well padded and will cause problems. As long as you keep humping heavy loads down hill you will be wearing your hips and knees out. It may sound like a worry-wart talking here but you should see my x-rays. You will end up like me unless you mellow out.
Best of luck!