Any brand that uses Japanese selvage in the heavier weights lasts ages. Take a while to break in and are $$$, though.
One thing that makes them last longest is washing gently and only when necessary. Tumble dryers and fabric softeners plus dryer sheets accelerate wear drastically. I have a couple pairs from Naked and Famous that are roughly a decade old with no tears or holes.
Otherwise like mentioned here: canvas pants or the firehose material ones from Duluth last a long time too. Much easier to maintain and handle frequent washing more readily.