I still do it. i love it because when something happens -- like short naps, night wakings, etc. -- I can look at my logs & usually puzzle out why. I've also really like it once we've started solids. It helps me see how much he's eating, if it's increasing, how his formula intake is, etc.
I think how long you do it depends on your personality. I bet if someone wanted to do a poll, you'd find that people who record are on one end of the spectrum Tracy talks about in her book (I think she called it "Wingers & Planners") and those who quit early are on the other end! I'm a Planner, so I enjoy recording!