I walked approx 15 miles last year, it took a few hours. Not too difficult if you really want to get to work. It depends on your motivation and dedication to your job of course.
It takes me about 50 minutes to walk just over 3 miles in good weather
to walk 15 miles in snow would take me about 5 hrs, probably more
that's at least 10hrs walking and 8+hrs at work leaving <6hrs to shower, eat, prepare for the next day & sleep/recouperate
not exactly something the average person would be capable of tbh no matter how motivated or dedicated