Why Do Automatic Watches Stop Working. For hand-winding and automatic watches I cant imagine thats of any use they will stop running after a period of time anyhow. It would stop on my wrist during an active day.

This may seem too obvious but it is a very common occurrence. The Battery has Died. Its fine for a few days but I definitely wont do that if I dont intend to wear that watch again.
Once it has even stopped on my wrist while sitting at a desk.
Yes a watch with an automatic movement will need to be manually wound periodically. Then took it. The vast majority of modern automatic watches run for 40 to 50 hours with the most common power reserve being 48 hours. That number can go up to three years or more with a quartz watch thats designed to run longer.

