How much to repair it? Do they flat rate it?
I have a Super Professional that only runs for an hour or so on a full wind.
https://www.calibre11.com/tag-heuer-super-professional/
Most Tag's, especially ones that are a few years old and older have base ETA 28xx movements in them. Quality movements with easily sourced parts and generally serviceable by any competent watch repair shop.
But when you wait for issues like that to arise, though, repair costs typically go up, and sometimes by considerable amounts.
Mechanical watches should ideally be serviced every 4-5 years, and never more than 8 years, regardless of how frequently you wore it. Seals dry up and the synthetic lubrication breaks down...soon after it's metal on metal contact for the geared surfaces. The ball bearings in the self-winding rotor also will go bad.
I know we all know "that guy" that's got a 20 year old Rolex that hasn't seen service... but i'd bet my bottom $ it runs like crap. I also hope they don't swim with it.