Watch winder should be on for roughly 8-12 hours per day, cycling through short rotations (30 seconds to 1 minute) with breaks in between. You don't need to leave it on constantly; some recommend letting the watch fully stop periodically.

Recommended Watch Winder Usage

1. Cycle operation: Use short rotation cycles of about 30 seconds to 1 minute, followed by breaks of 2 to 3 minutes. This intermittent cycling simulates natural wrist movement, prevents overwinding, and reduces mechanical wear on the watch.
2. Daily duration: For daily use, running the winder cyclically for 8 to 12 hours per day is optimal. This can be split into 2 to 3 sessions throughout the day.
3. Turns per day (TPD): Most automatic watches require between 650 and 1200 turns per day, depending on the complexity of the movement. Classic watches need around 650-800 TPD, while chronographs may require up to 1200 TPD.

Power reserve considerations:

1. Watches with a short power reserve (<36 hours) should be on the winder for about 12-18 hours per day.
2. Watches with a moderate power reserve (36-48 hours) can be wound for 18-24 hours per day.
3. Watches with a long power reserve (>48 hours) generally need about 24 hours on the winder to stay fully wound.

Additional Tips and Considerations

1. Avoid continuous operation over 24 hours without breaks to prevent overwinding and wear.
2. Some owners manually wind their watches weekly in addition to using a winder to ensure the power reserve is fully topped off, as winders may not always provide complete winding.
3. Using a high-quality watch winder with programmable cycles and reliable motors helps preserve both the watch and the winder’s longevity.
4. Many users run their winders overnight for about 12 hours, then allow a 12-hour rest period, which balances winding needs and wear mitigation.

This approach ensures your automatic watch remains accurately wound and mechanically healthy without unnecessary wear.