It will prolong the life of the Potenzas in calendar time, but probably not increased mileage on the tires. The Potenzas would only get more miles out of their life if for some reason they wore faster in the winter.
So it depends on exactly what you meant by the question, life in time or miles? I’m assuming you want to know what would be cheaper in the long run?
How many miles would you expect out of each tire, how much would the extra wheels cost, are you changing them yourself, and how many miles would go on each tire in a year. Add up the totals and you can figure out $/mile for each scenario.