When should you have your watch serviced? / Spring Q&A - Answering your watch questions

Q: When should I maintain my mechanical watch?

A: Generally, it is between 3 and 5 years.

　Some people say that maintenance is only necessary when the watch's original performance has deteriorated, such as when its accuracy has dropped significantly, but using the watch when it has run out of oil is not recommended as this will cause wear to the parts. Also, even if the mechanism has not run out of oil, if the watch has been used for several years, the gaskets should be replaced during maintenance or overhaul to maintain its waterproof performance.

Regular maintenance and overhaul costs by brand [2017-2018]

http://www.webchronos.net/features/18855/

From the watch repair site / antique repair workshop in Kobe

http://www.webchronos.net/features/22250/