I was my hands every time I use the restroom.
The longest I've gone without changing panties is probably like 3 days. But! [Sorry for the TMI] I wear panty liners and I always change those daily. But like if I'm really, really sick, I won't bathe so I won't change my clothes.
For most people it's gross if they don't wash their hair everyday because they're used to washing it that often. It's actually better for your hair to go every other day or even every third day with the washing instead. I haven't done it in a long time, but when I had my long, flowing, GORGEOUS hair I generally washed it every other day. It looked fine because my scalp got used to it.