The subject of watch servicing is an interesting one to watch on forums. It tends to bring out deeply held beliefs that sometimes defy logic, almost like a religion. For me personally, I don't care if other people service their watches or not. I was personally brought up with the idea that when you bought something, you took care of it, but that way of thinking has gone by the wayside to a great extent in today's throw away society. Also as an engineer, I was heavily involved in preventative maintenance programs, so that sort of mindset comes naturally to me.
From a professional point of view, I don't do all that many "maintenance" services, as most of the watches that come to me have some sort of problem. I'm certainly not trying to change people's minds, because there will always be the 10%-ers that won't change their beliefs no matter what. However there is one main thing people need to keep in mind when it comes to servicing...
There is no one size fits all answer that makes sense in every situation.
Different situations require different approaches to servicing. If you the type of person who primarily cares about costs, and you have a modern watch that you will be sending to the brand service center, then from an economic standpoint letting it run until it stops working could very well be the most economic option. It would depend on the brand, what they charge, how many parts they include in their base service pricing, etc.
For a vintage watch where the parts are discontinued, hard to find, and expensive, you are very often better off taking the steps needed to keep the parts that are inside the watch in good shape, so servicing before the oils dry up and the parts wear will reduce the service costs and delays looking for parts going forward.
How long a watch can go between servicing is not an easy question to answer. It depends on how the watch is used, so if it is worn daily as the only watch you own, it will likely need servicing more frequently than a watch that is worn in rotation with a dozen others than only gets worn a few weeks per year.
I have a Sinn 556 with an ETA 2824-2 movement in it in my shop right now. The watch was bought new 7 years ago and worn daily - not owned by a collector. On inspection I see oils that are dried up, and some that have failed and there are obvious signs of wear products in the jewels. Here are some photos to illustrate this - first the balance jewel was dry:
Here is the intermediate wheel jewel - note that the oil has turned brown, and there are products of wear in the oil that's left:
Same here in the third wheel jewel:
The oil in the seconds wheel jewel is completely dry, and the wear products here is in the form of a powder, rather than an oily sludge:
The escape wheel jewel has some minor signs of wear:
So let's look at the parts that are riding in those jewels - first the intermediate wheel - pivots worn on both ends:
Now the third wheel - one end not so bad:
The other lots of wear on the pivot - these pivots should be cylindrical:
How about that seconds wheel - I would say this one is well worn:
Escape wheel - there is some wear right up against the shoulder:
In addition to this both reversing wheels required replacing, plus the ratchet wheel driving wheel.
Now none of these parts are particularly expensive. Most train wheels for this movement are maybe $15 each, with the escape wheel being a bit more so this isn't adding a significant expense to the service. But as I mentioned, vintage is a different story. Here is a worn third wheel pivot from a vintage watch:
This part is long discontinued, but I did manage to find a brand new one - cost will be $150, so this one worn part will cost more than all the worn parts on the 2824-2 combined. On a vintage movement the parts cost can quickly rise to a point where it costs more to service the watch than it's worth.
So rather than sticking to dogmatic claims made by people on forums, I encourage people to think about things themselves, and do the research needed to determine what makes the most sense for the watches you have.
Cheers, Al
