Not exactly aesthetic, but I have found soccer shorts---specifically Umbros---to be nearly indestructible. I have a few pair that are more than 10 years old, although I've only ridded in them regularly for the past 2 years. I commute a couple of hours every day. I even wrecked in a pair and slid over (wet) asphalt and there wasn't even a tear in them.

For the cold, I go with roadie padded cycling pants; kind of queer looking, but they keep my legs warm and stay out of my chain.