One of the most common maladies affecting watches is magnetism.
When a mechanical watch becomes 'magnetized', the addition of a magnetic force to the micro parts, springs, and balance; the 'drivetrain' of the watch mechanism, creates additional resistances that cannot be completely overcome. The result is usually a watch that runs faster than it is supposed to.
It's incredibly easy to magnetize a watch unknowingly. While the refrigerator door is often called out as the usual suspect; the Bose Wave Radio, a sophisticated arrangement of magnets designed to look great on a nightstand, has to be very high on the list as well. Simply put, any time you get your watch very close to a small magnet or even a little close to a larger one, there's a pretty good chance that you are magnetizing it.
Watches with stainless steel cases are the most protected from accidental magnetism; those with gold cases, the least. Vintage watches are much more prone than their modern counterparts as watch manufacturers now consider the likelihood of exposure to magnetic fields when they design a watch.
Not considering the possibility of magnetism as the cause for a sick watch makes it likely that you'll pay for a lot of 'routine maintenance' and repairs that really aren't necessary. Not surprisingly, many watchmakers don't think of magnetism first when they hear about a watch that's functioning poorly... the 'surgeon' prefers to operate and replacing parts or rebuilding a movement is much more interesting than a quick and mundane demagnetizing.
A small and inexpensive compass is the go-to tool for detecting a magnetized watch. As you move the compass around the caseback, you'll be able to move the compass needle artificially if the watch is magnetized. If it isn't, the direction of North will never change!
If the compass needle points to a magnetic watch, then you can either take your watch to a watchmaker for a quick demagnetizing procedure or, if you own a demagnetizer, have access to electricity, and can push a button; do it yourself. The process is really simple. First and foremost, be sure that the watch you are about to demagnetize is mechanical and not quartz. Quartz watches should never be demagnetized! Mechanical confirmation made, follow this procedure: plug in the demagnetizer, place the watch, crystal side down on the middle of the 'target' area of the demagnetizer, push the red button... release.... push again... release, now turn the watch over (caseback down) and push the red button again.... release.... push again. Demagnetizing complete!
Magnets are everywhere so it's easy to over think this and become overprotective. Don't! If and when your watch has an encounter with a magnet that leaves it hurting, the fix is quick, inexpensive, and completely effective.