We certainly wouldn't recommend it. When used in warm weather, the softer rubber compound can wear out faster than the compound used in all-season tires. If you used your winter tires year-round, it would end up costing you more than switching between two sets of tires.
 

Let’s say tennis shoes. You could wear them all year round, whether you were on the beach in the summer or in the snow during the winter. But wouldn't it be better to wear flip-flops in the summer heat and boots in the frigid winter.