If anyone's wondering about the life of a pair of expensive Merino Wool tights, I've got the scoop:
I bought these in May of 2012. In August of 2012, I wore them about 15 nights on a bike tour as sleeping tights.
Then, I put them on underneath some pants in September and wore them every single day, 7 days a week, all winter until April when it warmed up. I used them sparingly this past summer as sleeping tights, and then in September I put them on again and wore them every single day until today, when I noticed a 1 inch hole in the crotch and retired them.
I estimate I've got about 300+ days and nights in them, and would not be surprised if it was closer to 350.
The threads along the seat and the center stitch in the crotch are wearing thin in rows, and there's a 1 x 1 inch hole along the center seam. Overall, though, they held up well- no seam failures at all and no substantial pilling. They got softer and softer.
I washed them in a washing machine about once every three or four days, using cold water and low heat to dry them. Since all the wear is in the seat, where they contact the seams in my pants, I would say that washing them did not contribute to their lifespan.
Obviously, I really like these. They got more use than any other piece of clothing I've ever owned. I have a matching top, but I wear these much more often.
For the $63 I paid for them on sale, I am enormously pleased with their performance. They lasted a long time and kept me warm and comfortable in so many different conditions, from windy 60º days to frigid -20º nights. I've hiked in them, sat for 2 days straight on trains in them, gone to rock concerts in them, and worn them to weddings underneath my slacks. They never built up an odor once in the entire time I owned them, even after 30-day trips.
I am going to try out Ibex Woolies 220 next to see if the durability is better. See you next year!