I had a similar situation, though I found out when at a BMW dealer for 4/50 warranty work. I was inquiring about an aftermarket warranty through the BMW dealer when they looked it up and told me. Call a BMW dealer and say you would like to check the CPO status of your vehicle. They can pull it up by VIN and let you if it has the CPO extended warranty as well as the "in service date" (therefore when it expires timewise).

Scott