well.. they last a long time..
I bought a pair from Scheels in Helena Montana back in the mid 70's . They saved my life in a snow storm in the Ruby mountains. I used them to hunt elk on the northern border of Yellowstone in January.
I am now on my third set of liners. cant find a reason to replace 'em
Most of my miles on these are from behind a snowblower in SLC and Chicago. I'd say they are not really acceptable as a hiking or extreme hunting type boot. They just don't have enough foot support for extended long range stuff. However they do two things very, very very well. They keep your feet warm and dry.