Almost 50 years ago when I first got married we lived in a somewhat ner-do-well neighborhood. The greasy biker guy upstairs (sans motorcycle) swore he never washed his jeans and they could stand up in the corner of the room by themselves. We moved to a nicer area in 6 months and I always made it a point to wash my jeans after a couple of days wear.
When I was in grade school, I wore my jeans until, yes, they were stiff as a board. My mother never mentioned it. Maybe she appreciated the lighter laundry load.