I shower about every other day or every day, depending on what I've been doing as far as exercise and stuff goes. I tried using some natural hair cleaning stuff (baking soda and then apple cider vinegar for rinsing), but even after a few weeks, it didn't really feel all that different, and it was a bit of a hassle using it, so I quit. I'm not a big "omg, evil chemicals"-person anyways, so as long as I can find a regular ol' shampoo I like, I'm alright with that.
But… How do you know that you don't smell? I mean, when we went to scout camps when I was younger, we would sometimes go for a week or even more without showering and no one really thought much of it (except that our hair got greasy), because no one had showered, so we were used to it. But it's kinda noticeable to people who aren't in the same situation. I mean, sure, if you stay in your room all day, then no problem, really, except that I'd personally feel filthy, but whatever floats your boat. But if around other people, I dunno, I feel like a minimum of personal hygiene should be upheld.