Just like a car, there is wear and tear from the watch running and also from the act of winding. Winding causes friction and wear in the stem and tube among others. Unless you are using a perpetual or other complication that is complex to set I let my watches run down or sit unwound until I wear them. If it's a watch you wear every day or every other day, then wind them according to the power reserve to keep it running. If it's a dress watch you wear once a week for a few hours then set and wind it when you are going to wear it. However, if you dont wear a watch very often it's not a bad idea to give it a bit of power once a week or so to keep the lubrication well distributed. I don't know scientifically if this is true, but it seems sensible to me.