I live in Minnesota and work for UPS, I also wear the full grain leather Danner mountain 600 boots. If you wear proper socks, they are warm enough for most conditions.

Edit durability: Mine are going through the third winter. They are probably in need of a new insole, and I am getting tread wear. They are not resoleable, so I'd say they are a 2-6 year boot depending on how much abuse and care you give them.