After about 400 miles my Specialized Roubaix developed a "knock" which turned into a pronounced "creak" after another 100 miles or so. I finally determined it to be the seat post by removing it and re-greasing the seat post clamp. The seat post has the words "do not grease seatpost" right on it, so I didn't.
The problem is that the knock came back after about 200 miles. About 2 weeks. I repeated the above and now its fine again. Is this normal? It seems a little to soon to me to have to re-grease. What could I be doing wrong?