The main thing is to have it pressure tested annually by a Rolex watch certified watchmaker, especially if it is a divers watch. The main reason for a annual check is to make sure that the case is waterproof. The test is free, if your watchmaker wants to charge you for it go to one that doesn’t.
A full service should be done every 5-7 years depending on use. Note it is not uncommon for oils inside the movement to dry out if the watch is exposed to harsh climates. Also gaskets in the case could dry out quicker with extreme exposure to hot and cold.
Visit our Rolex page HERE for more information.