This is the question we are asked most often, and it deserves better than a commercial argument. A winder is not indispensable. It is useful in specific situations, useless in others, and it is better to know before buying.
The three situations where it makes a difference
You alternate between several automatics
This is the clearest example. With three watches and one worn each day, each watch spends two days out of three unworn. Most calibres have a power reserve of thirty-eight to forty-eight hours. As a result, you have to reset the time almost every time you pick one up.
Your watch has complications
A simple date display takes seconds to reset. An annual calendar, moon phase or perpetual calendar requires a procedure that can take several minutes, with the risk of operating the crown during a time window when this is not recommended. A winder removes that problem.
You want the watch ready
A less technical argument, but just as valid. A stopped watch needs attention before you can wear it. A watch kept wound is ready to pick up and put on. For a collection you actually wear, that small inconvenience matters.
Cases where it's useless
A quartz watch. It runs on a battery; there is nothing to wind. A winder will do it neither good nor harm — simply nothing.
A hand-wound watch. It is wound using the crown and has no rotor. The same conclusion applies.
Only one automatic worn every day. Your wrist is already doing the job, and better than an motor. Save your money for a box.
And the question of wear and tear
The classic objection is that running a movement continuously causes premature wear. In absolute terms, this is true: a running mechanism wears. But a movement left stationary for months can see its oils migrate and thicken, which is no better.
The right balance depends on how long you plan to store it. For a watch you will wear regularly, even in rotation, a winder is a reasonable choice. For a watch you will not wear for several years, leave it in a box and arrange a service before wearing it again.
If you decide to take one
Allow some spare capacity and check your calibre's recommendations before setting up the device. We explain this in our self-winding guide.