most likely to fail is your desire to wear the pocketwatch
hypothetically

 

If you wanted to use a pocket watch daily and will have it periodically serviced, I would say it will outlast you. If parts are no longer available they can be fabricated. However, it would be up to you to say if you have an original watch after many services. For me, if the mainspring, crystal or some various gears are replaced during a service it's still the same watch. However, at some point I would think it's no longer the same, especially if more and more parts are scrounged from other watches or they're fabricated. Theoretically over time every part of that pocket watch could be replaced and there's nothing original left. Is it still the same pocket watch that you started with?

 

...Theoretically over time every part of that pocket watch could be replaced and there's nothing original left. Is it still the same pocket watch that you started with?

The watch of Theseus...

 

Pocket watches have proven to last indefinitely as we have witnessed in what is available from 1700's they will last as long as a watchmaker is available to maintain them.
most people don't realize that hundreds of millions of pocket watches were produced before the wrist watch was invented using a pocket watch.

 

Hypothetically, it will last indefinitely. The idea of servicing is to prevent damage from happening in the first place - if damage happens, that's repair, not service.

Very few people (in my experience) actually service watches before they need repairs. With a pocket watch that likely doesn't seal very well, you would need more frequent servicing than say a well sealed wrist watch, because a pocket watch will get contaminants inside it more easily, and those can accelerate wear.

I would expect that some parts will need replacing even with proper preventative maintenance, primarily the mainspring.

Cheers, Al

 

Since pocket watches are not water resistant, moisture and dust can get inside, so maintenance might be required more often than a water resistant wrist watch.

 

Longer than you might expect from it.

 

I have worked on American PW that are over 100 years old, which ran "in spec" after service.
If there are no worn or broken parts, and the watch is serviced every 3-5 years, one should easily expect 100+ years.
That said, blued mainsprings will require periodic replacement (as part of service)...which is not necessarily a "wear" issue so much as a "set" issue. Later RR grade (and other) pocket watches were equipped with alloy (eg Whitealloy) mainsprings from the get go...so these should last almost indefinitely. Blued ms can usually be replaced with a suitable alloy ms...attention must be paid to select a strength which does not cause excessively high amplitudes resulting in rebanking.
Regards, BG

 

Starting with a good quality, at least 17 jeweled movement, the most likely part to wear would be the winding crown. Over time the knurling will wear away making winding difficult. Next, I think would be the winding parts, specifically the winding pinion to crown wheel, also the sleeve in the pendant.

Probably the worst thing that will happen to the watch is it getting serviced. Parts get scratched and bent; or worse yet, get broken. Screws get stripped. Some folks think they can improve performance by tinkering with the escapement--this assumes it was correct at the start.

 

Eastern and western thought has differed on this. In the west, it is more common to believe that the the watch of theseus' "essence" derives to a great degree from the originality and provenance of parts of the whole. So say as long as some % of the parts in the watch are original, it is still theseus' watch. In japan, to the contrary, essence derives from use and function. There are temples that are thousands of years old wherein every board has been replaced dozens of times. It is still considered 100% original. So long as there is a continual lineage of function, itt would still be considered theseus' original watch, no matter how many.parts had been replaced.

There is no right answer, of course. The only constant is proper service intervals.

 

I have a 1918 Illinois Watch Co. Ramona full hunter pocket watch that still keeps decent time