Your piss dribbles and farts go into your pants in general. If you choose to go commando then so be it, I (unlike you and Norn) am not the clothing police.
I should point out that the latest episode was merely an experiment following the pre-printed guidelines provided by the jeans manufacturer who specifically said wear for 6 months before washing.
Being extreme I did the denim equivalent of turning the switch up to 11 and went further, 7+ months.
Normally speaking I would go around 3-4 months.