I do a lot of backpacking in the summer with my wife, and I wouldn't wear polypro on any of those trips unless I wanted to be thrown out of the tent at night. Polypro really smells bad after a few days. I have polypro that I wear for skiing or 1-2 day hunts, as it is lighter and seems more durable than merino. The first day out on our backpack last summer, I made the mistake of sitting on a rock when I was changing into my Smartwool longjohns. It started a small hole that had expanded to about an inch across by the end of the trip.