I'll chime in here too...
I bought a set of OEM sensors with reset tool from an online Ford parts dealer, and had them installed when I had my new winter tires mounted on rims last month. I put on the winters Saturday and still have not had a tire warning/light. I've driven the car about 4 times since and have put on 100 kms in that time.
My 3 season wheels/tires are stored 4 floors away in the storage room of my condo.