[dave_universetf]

There is also a feeling by some horologists and watch fans that the hack interacting with the balance oscillator and suddenly halting its motion is detrimental to the movement's health and precision. I haven't found any data to substantiate this, but I'm told that some watch aficionados prefer non-hacking movements for that reason.

[ksaj]

I can imagine this being the case, but the mechanics tend to be so accurate that I could see either being the case. I think the start/stop action is so quick that it likely is not damaging. But I'm clearly not an expert on this.

Another thing - in the comments someone mentioned military folk using hacking watches to sync their watches together. This use case I do know about, although for civilian purposes. We used to do it as kids, and became well aware of just how inaccurate all of our kiddie watches were. We used to sort of race them if our day was long enough. But they were accurate enough for our various games.

[dave_universetf]

It does seem a bit silly to me as well, given the stresses that watch movements are subjected to day to day, and that the hack's mechanical design barely touches the balance at all. It doesn't take very much friction at all to halt these movements, so I struggle to see where the source of damage would lie. But, people have their opinions.

And yeah, mechanical movements are technological marvels, and can keep incredible time for being a completely analog machine... But seconds per day is still about as good as it gets unless you take expensive measures (like the marine chronometers did) to get diminishing returns. And less expensive or well tuned movements can easily drift by a minute or two per day.

In a way, we've been spoiled by quartz and electronic timekeeping. Now that GPS blankets the world and lets any timepiece continuously synchronize to within microseconds, "seconds per day" sounds ludicrous. And yet, it built empires and ran the world for a couple centuries! Especially for civilian use, it's rare to truly _need_ better precision, aside from the general desire for perfection.