Why does my automatic watch run down in less time than the stated Power Reserve?

'Power Reserve' means the number of hours the watch should run from being fully wound up. But a common mistake with automatic watches is to wear them only a few hours a day, or every few days, and think that is enough movement to keep it wound. Many automatics need at least 10-14 hours a day of wearing with you moving normally (more than watching TV or napping). Even then, the watch may be far from fully wound at the point you take it off at the end of the day, so may not continue to run overnight or over a full weekend. How much you wear the watch over weekends is important too, as people's behavior is often different them, often leaving the watch much more or mush less wound by Monday.

To test to see if your watch is really getting its full power reserve, try this: manually wind your watch at least 40 turns and make sure the time is correct. Then leave it on the dresser for two to three days and see what time it stops. If it runs for close to the stated power reserve (usually 40-44 hours for many modern mechanical watches), then your watch is perfectly fine. If it runs significantly less than that, it may need cleaning or an adjustment.

If your power reserve is functioning correctly, then you may need to simply manually wind the watch when you take it off to ensure it is sufficiently wound. Or you may choose to change your wearing habits to keep the watch on your wrist for more active time. And finally, you can always consider getting a watch winder to keep your automatic watch ready to wear even when you do not use it regularly.