If the rubber is wound to near maximum turns flight after flight, performance of the rubber will suffer. Not using the rubber for a period of time will allow it to recover some of the lost performance. Modern rubber is better in this respect than the rubber available 20 years ago. When the rubber unwinds, there will be much more power available in the first few seconds than during the rest of the motor run. The winder has a crank that turns gears, this turns the rubber motor faster than you turn the hand crank.
Rubber is stretched so that it becomes thinner and more turns can be cranked into the rubber.
To get maximum turns in rubber, the rubber is stretched to a length of 3 to 4 times the un-stretched length. To extend the life of the rubber and for smoother unwinding, the rubber should be lubricated before winding. Many things have been tried but silicone based rubber protectant such as Armorall or Son of a Gun are easy to find and use. The rubber motor is placed in a plastic bag and then the rubber protectant is sprayed in the bag, the rubber is worked inside the bag. Armoral rubber protectant available in automotive stores.