When I was a hairy biker we didn't wash them and after six months or so they went black and shiny but eventually rotted through. It is a good idea to wash jeans.if you don't wash them surely the must start to smell like pee or man sweat from your balls.
even if your changing underwear everyday in the heat the sweat of your balls must evaporate and condense on your jeans.
I always wash mine every 1-2 weeks, dye them once or twice a year, they still look new.
is not washing jeans some goldmine talk from when people literally scrubbed clothes on a hard abrasive surface to clean them?