I started shaving when I was a freshman in High School, because I was in MCJROTC and hair's basically a no-no. Junior year I was rocking the immature idiot chin-beard look that I didn't trim until it got too long to stand, at which point I'd shave it off entirely and start again.
Now-a-days, I can actually look reasonable with two or three days stubble, but before I was shaving once a week simply because the stuff wouldn't grow back fast enough to look terrible.
So I guess I'd say: 14/15 whether you think you need to or not. I didn't think I needed to until I started shaving and noticed that hairs were growing back where I hadn't. I STILL remember how weird a clean-shaven upper-lip felt.