What you may not be accounting for is the tradeoff you are making for ability to hike as you get older. There is no doubt whatsoever that you are trashing your knees. You may be blissfully unaware of it until the day your cartilage is completely worn through but be assured that that day will arrive much sooner than would have been the case carrying lighter loads.

It may be that have consciously made that judgment and the opportunity to do the fantastic hikes you are doing is worth a shortened span of being able to get on the trail at all. It is, a matter of HYOH, after all.