As we wear our Rolex regularly they catch dirt and pollution. If you check the face of the watch itself it looks very dirty and is often scratched. And if the dust enters the watch case it can cause the gears to block or can affect the movement. Thus there is need to clean your rolex to make them work. It was said that watches should be cleaned every year, but the quality of the oil has improved and most people don't live in as dirty an environment as they did when people used horses to get around town and heated their homes with coal. If you are using your watch on a daily basis, you should get your watch serviced when you first get it and every couple of years thereafter. Water resistant watches can usually go 3-5 years, but if want to count on it being water resistant, you should have the seals checked every year. You should get your watch cleaned immediately if the insides ever gets wet, or even if you just see moisture forming on the inside of the crystal.
There are pros and cons involved with having a watch in your collection cleaned. Every time a watch is worked on, there is a certain risk that something will be broken or lost. Many cleanings will also dull the finish on the parts, and this is especially true for two-tone finishes. Cleaning will often also clean off some of the paint in the lettering on the movement. And, of course, there is the added expense of having a watch cleaned.