Since I'm a girl, I generally keep quiet about this as girls are supposed to be super clean kinda thing. I'm clean, but I rarely ever wash my jeans. I always find my jeans so beautiful when I first get them and I know they will be ok after one wash on cool and no drying, but I still rarely ever do it, unless I have got them dirty or they really do need to be washed after a long time. I think the only time to worry about washing is if they are coated and waxed as that can peel off or if they are rusty washed with dirt etc which could wash out like some of the old Diesels. Otherwise I think it's fine, just keep the water cool and don't dry them, let them hang dry. I think though in general as long as you are clean, you aren't really going to make the jeans dirty, only with a bit of sweat, but then that's your own bodies bacteria anyway so it's not harmful, would only cause odour after a while lol!