How Often Should a Watch be Serviced?

Running a watch without service, cleaning and fresh lubrication, is very much like running a car without changing the oil.  A watch may be said to "run fine", but if it has not been cleaned then grit in there is grinding away at the moving parts.  It may run fine, right up until it doesn't, and by then something that was fine before has been damaged.

Long ago, the oil used by watchmakers was organic (from sea animals).  This oil naturally became gumming over time. When it was idle, that is to say when the watch is not run, this process accelerated.  This is the origin of the idea that watches should be run at least periodically to stay in good condition.

With modern oils this problem is greatly reduced.  The life of new synthetic oils is practically indefinite in some instances, but at least many years.  And the oils hold their condition even when not regularly compressed.

So this leaves the issue of dirt getting it, landing someplace it should not, and grinding at moving parts.  Antique watch cases do not seal in any sense, so dirt does get in.  How much of a problem this is depends on how the watch is stored and used, and how frequently it is carried.

Following on from the initial service, the watch will definitely require service at regular intervals, if it is going to be used. If the movement is run very frequently, a cleaning and lubrication should be done every 3 to 5 years. If a watch is worn only on limited occasion, and stored in a clean, dry manner, then every 7 to 10 years should be fine.

Once a watch is initially cleaned, so as to get the old dirt and gummy old oil out, and make sure there is no moisture issues, it will not get any worse by just sitting.  A watch carefully stored and not run will be fine for a very long time into the future.  So, if a watch is part of a collection or a display item, and is perhaps wound from time to time, but not carried and not a "working watch", then it isn't necessary to regularly service the watch.