It is a micro-machine, and requires regular service to avoid damage and to continue proper function. This is usually a period of between 4-6 years. Depending on the environment the watch was worn in, and what type of watch it is will affect any service parameters.
Older Antique and Vintage watches were quite often marked "Water Proof" or "Dust resistant", but these are quite often anything but, so dirt and moisture will find their way inside. A dirty watch cannot be oiled, and you cannot clean a watch without completely disassembling it.
Modern fluids are used in watch cleaning, and modern lubricants extend the life of the watch far beyond it's original intended useful period. When lubricants dry out, they leave behind a residue which attracts dirt or by itself may act as an abrasive. Dirty, dried out watches should not be run, as they can be damaged.
Even rubies can be worn away by dirt and friction, and will leave behind a microscopic pink dust, which is highly abrasive itself.
Not every watch can be salvaged through a long overdue service, but improvement and protection are invariably achieved. We see watches dating back to the 18th century, and everything in between. Small watches from the teens and twenties are often the most badly damaged and worn out, as they passed through the Depression with no service and many years after. Radium dials can often be found on these watches, and we do not re-lume these dials. Even if a dial no longer glows in the dark, the Radium is still pretty much as hot as the day it was applied, with a half life of 1601 years. The Zinc Sulfide no longer glows in the presence of the radiation, but the radiation is still there.
A full watch service, including full disassembly and cleaning, with reassembly and lubrication and demagnetization, as well as regulation is known in the trade as a 'CTR'. Good quality modern watches with chronometer spec can be kept in good condition for many years with regular service. Even watches that have been neglected can often be repaired and brought back to acceptable running, depending on the damage and availability of some parts. When necessary, we make our own parts.
Our service also includes a thorough cleaning and polishing of the case, and bracelet refinishing is available.
Contrary to popular belief, Quartz watches are more fragile than mechanical watches. Even small amounts of dirt or moisture can damage or stop a quartz watch, and magnetism will destroy them. They have much shorter life spans, and these can be as little as one year for very cheap watches, to approximately 25-30 years for good quality ones. In contrast, a mechanical watch can last hundreds of years, and the good news is, mechanical watches are here to stay. In hot and humid countries for example, quartz watches do not fare well, and mechanical watches are the norm.