Bulova 1963 Jet Clipper

Overwinding is a myth.

If a watch or clock is wound up tight but does not run, that is an indicator that something is wrong. With clocks, the wear and tear is metal- on- metal, and at full wind the mechanism is telling you it is worn to the point of jamming. 

With watches, there are jewels (usually) to mitigate the wear, but these can also get full of dirt or the lubricant will dry out, and the watch stops. With automatic watches, the loss of eleasticity and wear of the mainspring against the barrel can cause 'mainspring creep,' which means the watch does not wind itself properly while worn. Hand winding these can sometimes make it worse, especially if you hand wind them to full and cause the mainsring to slip on a regular basis. This additional wear to an already worn system will eventually cause the watch to not hold much power at all. 

There is braking grease on the inside of the automatic watch barrel, and when that dries out, the wear of the bridle against the walls of the barrel is increased. Mainsprings also become 'set,' which means they no longer have the same modulus of elasticity and therefore less power. 

There are 200 reasons why the watch stops, as Donald DeCarle used to say. Lack of service leads to all kinds of issues. 

I'm going to invent a time machine and go back and find the guy who originaly made up the overwinding myth. I have heard this thousands of times in my shop by well-meaning customers, and it is one of those stories that just gets perpetuated, like the one about car batteries on a concrete floor.*

*OK, before anyone asks, batteries do not slowly discharge because they are on a concrete floor, they discharge because there is a buildup of dirt and gunk on the top that has electrolyte in it or electrolytic properties, causing a small, drawn out short circuit. This has been debunked many times but keeps springing back up like a King Dandelion in your backyard...