I agree these are great pants. I have had them for 3 winters and they are still going strong. I don't ride as much in winter, perhaps once maybe twice at most per week, but these make it possible. I recall some were complaining that they were not available last year at REI, so it is good to seem them again.

However, I don't think they have to be limited to temps 40F and above. I have worn them in temps in the 20s or so, perhaps even in the teens. Once it is in the 30s, I will wear a very thin pair of long underwear and that does the trick to keep me warm. Because the Headwind pants are rather loose, they can easily fit a thin layer of long underwear, it does not take much of an underlayer to be comfortable in temps below 40s because your legs are doing a lot of the work to keep you warm.