I never use to, but ever since I stopped shampooing every day I started conditioning regularly. I don't even have long hair, but my hair is a lot nicer as a result.
I have oily scalp...so that is a huge no.
eh depends;
If you're a guy with short hair, on days you don't exercise there's really not a reason to shampoo your hair. I go to the gym 4-5 times per week, and I shampoo on those days, and not on the others. My hair is much softer and shinier looking since I started following that pattern. If I'm going to the gym a lot, and thus shampooing my hair more, I will use conditioner a few times per week