I wash my jeans every 6-12 months, with occasional febreezing after I wear them. This is way more convenient than having to wash and iron my other pants.
> Last year a microbiology student at the University of Alberta, Josh Le, wore the same pair of raw denim jeans for 15 months without washing them and then tested their bacterial content.
He tested them again two weeks after washing them and found the bacterial content to be much the same.
> "This shows that, in this case at least, the bacteria growth is no higher if the jeans aren't washed regularly," said Rachel McQueen, a professor of textile science, who worked with Le on the informal scientific experiment.
I've done basically the same thing. Definitely passes the sniff test - somehow there's not much of a difference. Not sure if oil from the skin ends up becoming a antimicrobial agent over time?
FWIW mine need a wash after ~4-6 wearings or they smell. I haven't tried the vodka-spritzing trick I've read about, though, which may let them go longer.
How they're stored probably affects it some. I have better results hanging them up rather than letting them sit on the floor, even if I'm just going to put them back on the next morning.