think of it like milk

Hi Thomas,

Milk can be kept under ideal conditions for 14 to 17 days before it goes bad. Regulations require a "sell by" date that is somewhere between 4 and 9 days, assuming that most folks will drink it within a week or so after that. It doesn't mean that it goes bad in 4 days, but it's a pretty clear indication that it's gonna bad in less than a month.

If a lubricant manufacturer knows their lubricant is effective for 15 years, they might give an "only store for" recommendation of 5 or 10 years, but not 6 months to a year. Of course we can assume that the lubricant manufacturers want to sell more lubricants, but watch companies do in fact pay attention to how long watches run on average, so if the lubricant companies GROSSLY underestimate how long lubricants can be stored before using them, it wouldn't take too long before the watch companies would wise up and take those recommendations with a large grain of salt. That is not happening.

In fact, the companies that are serious about quality service are continually taking a closer look at proper lubrication storage and application to see how the processes can be improved in the interest of lowering the incidence of warranty repairs, lower the comeback rates and generally extend service intervals.

I know there are wathc collectors out there who believe that the 3-5 year service interval recommendation is just a scam to get more of our hard earned money, but for the most part at least, this is absurd. It's widely understood within the industry that running aftersales service in the black at all is a real accomplishment. It is not by any stretch of the imagination a cash cow and is valued primarily as a way to support the brand image and sell more watches (where the money comes from).

A recommended service interval is a way to manage expectations. If you know that some substantial percentage of the watches you make and/or service will fail after 4-5 years, it behooves you to let your customers know the recommended service interval is 3-5 years. That way when this substantial percentage of watches do stop, the customer will not be quite as furious as he/she might've been otherwise. If you tell your customers your watches run for 10 years between servicings and 70% of them stop after 7 years, you're gonna have a customer service nightmare on your hands and/or will bankrupt yourself with complimentary services.

OK, so back to the lubricants. A watch will run for 3-5 years on average not because tremendous loads or extreme heat are grinding away at the oils and greases inside. I mean sure, there is some degree of molecular shear taking place, and the wear of the metallic components is generating particles that are contaminating the oils and making them less effective. But the real problem is oxidization. The oils are simply drying out. Of course as they dry out the problems of shear and contamination are accelerated tremendously as well.

And yes, the amount of air inside a sealed wristwatch is plenty to oxidize the tiny fractions of a millilitre of oil found in the various bearings. And no, a watch case is not perfectly air tight anyway. Water resistant (even to great depth) is not the same as air tight, and over time the gases inside the case are circulating to some extent (arguably very, very little in a diving watch).

I am not a materials scientist, a chemist nor certainly a tribologist. Take all of the above as conjecture and supposition based on what I've actually seen in watches in service. And no, I do not have the many years of experience that some practicing watchmakers have, but I have had the good luck to work for companies and be put in positions that allow me to examine a LOT of watches personally as well as look at a LOT of data about warranty issues, comebacks and other technical and service issues.

_john