It is generally accepted in the industry that a watch should be serviced every 3 to 5 years.
In reality, this rarely happens as many owners have a ’If it’s not broken, it doesn’t need fixing’ attitude, but that is a generally accepted guide.
Another common question would be regarding watch storage and what can happen to the lubricants over time.
Many would argue that the lubricants could degrade over time and this is quite likely. However, it does depend on the quality and type of lubricants applied to the watch movement.
It is also suggested that lubricants can evaporate. Whilst I am not an expert on synthetic or mineral oils, my understanding is that this is not likely, but with the watch sitting stationary for extended lengths of time, it is possible for lubricant to creep away from it’s intended application point, leaving it dry.
If this were to happen and the watch is brought back into action without service then it may not perform as it should.
If storing the watch it’s advised to wind the watch at least once per week, and if it’s an automatic then an automatic winding machine is a good way to accomplish this.