I will start with this somewhat strange comment: A good watch needs to be consistent rather than accurate.
"A marine chronometre is a timepiece that is precise and accurate enough to be used as a portable time standard" (Wikipedia). The important words are "accurate enough" and "time standard".
All mechanical timepieces have errors and inaccuracies. Many non-belivers have suggested the solution is thermo-compensated quartz.
Absolute accuracy (while important) is not as important as the consistency of the inaccuracy.
Seamen and adventurers have staked their lives on the consistent errors of their marine chonometres. This is one reason they were locked in a box, so they could not be adjusted during the journey.
As wristwatches became popular, this inaccuracy was compounded by the gate of one's walk or the speed of one's step. Older people tend to be less active than younger people and they often complain that their automatic watches will not wind.
Everyone wears their watch differently and this is the challenge for accuracy and consistency.
A watch is a mechanical marvel with many moving parts. Its' wheels, cogs and teeth all wear, "bed in" or settle into their own rhythm over time. Its' time keeping changes and the time piece mellows with age.
Strange as it may seem, good audio, amplifiers, DAC's etc. also change their behaviour/sound after being operating for some some hours.