So I tend to go on long trips, and I end up going 3-4 weeks without a shower if I'm off sailing or camping in the deep woods or whatever. Edit: of course I do make sure to get naked and air out regularly, if I'm not able to wash.

Don't get me wrong, I'm sure that I get pretty funky, but I've never gotten jock itch or anything. No skin conditions.

I think a lot of modern "hygiene" standards have less to do with hygiene and more to do with selling people more crap. Actually, the only time I remember having skin issues was the three months in 8th grade equivalent that I used deodorant. Once I stopped that, all the irritation went away.

I occasionally ask people around me if I smell, or if it's obvious I usually only shower 3-4 times per week, and most people are surprised to find out I shower 3-4 times per week and don't wear deodorant.

Edit2: diet also plays a huge part. I tend to eat almost exclusively rice, beans, and veggies. I recently let a friend who had some shit going down live in my basement for six months, and his primarily junk food diet definitely did a number on both odor and my toilets. I didn't even know that level of mess was possible in six months.