In an interesting thread on the Military Watch Resource forum comparing the Seiko caliber 6309 to the ETA caliber 2824, shortwave said:
I have a 25 year old 6309 7290. It hasn’t been cleaned in at least 10 years. It advances 1 to 2 seconds in 12 days. I’ve never seen such accuracy in any manual watch. The ETA in my Marathon, gains seconds a day.