The pitch sounds reasonable enough. You own an automatic watch. Automatics need motion to keep running. Therefore a small motorized box that gently rotates the watch when it's off your wrist is, logically, a good idea. The problem is that the logic skips a few steps, and those steps are where the real answer lives.
Start with what an automatic movement actually wants. The rotor inside spins as your wrist moves, winding the mainspring. A fully wound mainspring will run the watch for somewhere between 38 and 80 hours depending on the caliber, with most modern movements landing in the 40 to 70 hour range. If you wear a watch daily, or even four or five days a week, the mainspring rarely drops to zero. The watch keeps time, the date stays current, and life is uncomplicated.
The winder pitch starts to make sense in two specific situations. The first is the rotation collector, someone with five or six automatics who wears each one only occasionally. Every time they pick up an unworn piece, they're resetting the time, the date, and possibly the day, month, and moonphase. For a simple three-hander this takes 30 seconds. For a complicated watch it can take ten minutes of careful crown work, and crown work done in a hurry is how stems get bent and date wheels get crunched at the wrong hour.
The second situation is the perpetual calendar. These movements track the date through leap years using a mechanical program that, once set correctly, theoretically never needs adjusting until 2100. Letting a perpetual calendar run down means resetting it, and resetting a perpetual calendar is one of the more nerve-wracking things you can do at a kitchen table. Some require a service visit if set incorrectly. For an owner of one of these, a winder is genuine insurance.
When a Winder Is Doing Nothing Useful
For everyone else, the math gets thinner. A single-watch owner who wears their automatic five days a week does not need a winder. The watch is on the wrist when it matters. On the weekend, it sits, and on Monday morning a few shakes and a couple of crown turns bring it back to life in under a minute. That is not an inconvenience worth solving with a $400 box.
Two-watch and three-watch owners often fall into the same category. Rotating between pieces is part of the fun, and resetting a simple automatic takes less time than choosing which one to wear. There is also a quiet argument, occasionally raised by watchmakers, that a movement spending some time at rest is not necessarily a bad thing. Lubricants settle, parts aren't under constant load. Whether this matters in practice over a service interval is debated, but it does undermine the idea that constant motion is inherently better.
Then there's the wear question on the winder itself. A cheap winder running 24/7 is a small motor and a set of bearings doing exactly what small motors and bearings eventually do, which is fail. The failure mode is usually harmless (the winder stops, you notice, you replace it), but the cheaper units can also develop a vibration or a pause-and-jerk pattern that's arguably rougher on the watch than just letting it stop.
What Actually Matters If You Buy One
If you've worked through the above and decided a winder earns its keep, the buying criteria are pretty narrow. Turns per day (TPD) settings should be adjustable, ideally between 650 and 1,800, because different movements have different winding requirements and a winder stuck at one speed is a winder that's wrong for half the watches you might put in it.
Direction matters too. Some movements wind in one direction only, some bidirectionally. A good winder lets you set clockwise, counter-clockwise, or alternating. The cheap ones often run one direction at a fixed speed, which works for some calibers and quietly does nothing for others.
Build quality shows up in the motor noise and the cuff that holds the watch. A winder you can hear from across the room is going to annoy you within a week. A cuff that's too tight stretches strap leather; one that's too loose lets the watch slip and tap against the housing. The mid-tier brands (Wolf, Orbita, Barrington at the entry level) have largely solved these problems. Generic Amazon units often have not.
The honest summary: a winder is a tool with a narrow but real use case. Perpetual calendars and rotating collections of complicated watches are where it pays off. A daily-driver automatic on the wrist of someone who actually wears it does not need one, no matter how good the walnut veneer looks on the dresser. Buy the winder if your collection asks for it. Don't buy it because the watch came with an empty space next to it on the shelf.