This is a question that most of the non-jeweler Rolex AD can offer, and most of the people do not know that there is the right for them to SELECT a better Rolex when you buy new from Rolex AD.
Well, most of the WATCH dealer like Zurich, Oriental, Wah Hing can have this service. Do to forget that you are spending some money that is good for buying a used BMW, this is your customer right to ask for the Shop to provide you a Health Check on your Rolex.
As you know you Rolex is a Certificated Swiss Chronometers, that can guarantee some kind of time accuracy per day.
Usually I will buy a Rolex with +2 second per day base on a temperature of 25 deg C,
And some time you can get one like +5 seconds a day, it is still within the specification of qualify the watch to be a Chronometer.
The reason why we have to buy a watch faster a few seconds is that after a few years say three, the lubrication oil inside the jewel bearing and the minor wear and tear inside of movement will gradually add on some friction that would slow down the watch.
So when you use your Rolex it may be becoming slow after 4 year, then it is time for you to send it to Rolex Service Centre for a cleaning..
Actually the period of time for Overhauling or cleaning depending on how you use the watch, and some of my Rolex has been using for 10 years still working in perfect time keeping.
So next time when you go to buy your Rolex, ask for the time check service, of course it is Free!