I voted for every other day for a personal reason. When I was younger and ate eggs and or mammalian meat, I had body odor most of the time. About 6 years ago I became a vegetarian in order to reduce my triglycerides and cholesterol. Over a period of two months my blood tests and need for deodorants went away. I do bathe every other day to minimize fungal infections due to sweating while exercising. .
It depends. I am very active so I usually have to shower my body every day, unless I didn't do much that day and didn't sweat. My hair seems to stay clean for a while, so I wash it at least every other day. Maybe a couple days longer if it hasn't gotten too bad.
I shower every night before bed...I can't stand sleeping with dirty hair. As newlyweds, my wife and I would often shower together.