Mechanical watches, unlike quartz models require regular maintenance to continue working perfectly for years.Without this sevice the lubricants in mechanical watches deteriorate and the internal moving parts start to wear out, leading to, initially bad time keeping, and then to total failure.Electronic quartz watches that have no moving parts don’t need servicing, but quartz movement watches with moving parts are subject to the same problems as mechanical or automatic movement watches.Obviosly if your watch has a low value then servicing is either a diy thing or dont bother, run your watch till it drops and then buy another. Servicing a watch can be a very expensive thing to do, especially from name brand servicing centres. Example:to service an Omega watch can cost from $400 for a quartz model upto $800 for more complicated watches.This includes replacing all the necessary parts to ensure perfect or as new working condition. A full service on a Rolex includes changing many parts and all the rubber seals and undergoes many tests to make sure it runs like new, can cost you more than $700.When you send your watch to be serviced by the brand service,they will replace all necessary parts,even if they are still in good condition,to ensure your watch works perfectly for the next 3-5 years and this work is usually covered by a years guarantee and therefore can be expensive.Most watch manufactures reccomend sevicing every 3-5 years.For the luxury watches, servicing is almost obbligatory to keep up the value of the watch. As the value of the watch drops ,one has to balance the benefits of expensive in house brand servicing with all its guarantees or opt for servicing by an independant watch servicer.The independant watch repairer will charge you for the level of service you request.This can be from cleaning and lubricating only, and upto a full service replacing all worn parts.But there wont be any guarantee on parts not exchanged.As the watch value lowers, real watch servicing, becomes harder to justify.It may be easier to replace the whole watch mechanism than replace single worn parts when servicing costs are low. Watches under $150 usually as far as servicing goes is limited to cleaning and lubricating by independant repairers.
To recapitulate; main brand dealer servicing is best but at a high cost and only worth doing on expensive watches. Middle priced watches ,get an estimate for the work to be carried out before servicing by an independant, explaining exactly what they will do to your watch in their service. Watches between $70-$150 only have cleaned and lubricated,and when they break replace the whole mechanism or buy a new watch.Under$70 only clean or diy servicing.