The duration of a ski boot's longevity depends a lot on the quality of the boot as well as how many times you use your boots per season. An aggressive skier that skis 90 season days will most likely have to replace the boots after a season or two whereas the fairweather skier who hits mellow slopes only 20 days a year or less may be able to get five or six seasons out of a boot. In general, ski boot manufacturers recommend replacement after 150-200 ski days.