One to clean, one quick rinse before bed. I have long hair and pollen allergies, I have to rinse off.
Daily. But that's my skin for you - it cracks or gets raw spots easy, so even though there may be good bacteria, there's also bad, which I have to keep out of those raw spots - skin infections suck
I shower each night before workdays. On weekends if I haven't done anything particularly dirty I skip a night (sometimes two). I never understood why ppl shower in the morning (aside from getting sex stuff all over them). I like to get into my bed clean and there is nothing I do during the night to make me less clean by morning.
Sweat is mostly salt water and dries. I bike six miles to work in this South Florida heat and humidity - my shorts and T-shirt are soaked. But it dries and I put on my work clothes without taking a shower and there is no odor as ppl would suspect.