When I was about 10, my boyfriend of the time (someone I swapped love-letters with, basically) wore the same pair of jeans for a month straight. I dropped him around day 10 through disgust. But 15 months? Now that's science.
College student Josh Le wore the same pair of jeans for 15 months, racking up 330 wears of the $165 Nudie Jeans while studying at the University of Alberta. Every now and then he would give it a sniff-test, and if he detected a slight pong he'd stick them in the freezer for a few hours.
After the lengthy test-period, Le and his professor swabbed the jeans, then finally washed them. He then wore the jeans for 13 days, after which they swabbed them again—and discovered that bacteria-levels were the same regardless of the length of wear.
Now, I do have a couple of issues with this experiment. After 15 months of continuous wear, the bacteria and stains were probably so steeped in the fibre that just one wash probably wasn't enough to get it all out. What they should've done was swabbed the jeans after a few days' use, before the lengthy test started.
Also, 13 days? Who wears the same pair of jeans for 13 days and considers that a normal wear-period? Perhaps after you've donned the same trews for 15 months, but I consider five wears to be the maximum before needing a wash.
Image Credit: This Is Awkward