Geez people, theres nothing wrong with his tires, tubes, rim tape, or anything. He said it deflated over a couple of weeks. Ever notice that a balloon will slowly deflate over a period of several days....well tubes do that too..its perfectly normal. They are not perfectly airtight.

To the OP: There's nothing wrong with your tubes. Save your money and stop buying tubes. You should top off your pressure every week or sooner if you are particular about your tire pressure. The reason skinny little road bike tires deflate rather quickly is because of their small volume. A small amount of air loss will quickly lower the pressure. You may notice that mtb tires will hold their pressure for longer, and a car tire will hold its pressure way longer. Thats because these tires have much much more volume than a skinny road tire and a lot more air needs to leak out before you will notice a pressure change.