Comment by mmcgaha

My father's Seiko from the late 70s still keeps time at around 30 seconds per day. It has never been serviced so I am sure it is bone dry and really should not be run. I regularly wear a 2015 Seiko that used to be 8 seconds per day fast but has fallen to 5 seconds per day slow so it is probably time to service it. My two newest watches are from 2017 and 2021 and they are consistent since break in. So given my limited number of data points, I would say 5-7 years between service but if you just want to wear it until it dies, 10+ years is probably reasonable.

On a side note, I have read about 40 year old Seikos being worn daily without service but that sure feels outside of the norm.