We don't listen to radio when traveling. In 2007, we bought a MH with a 12 month free subscription. We turned it on a time or two and forgot about it. About 2 or 3 years later, we discovered we still had SiriusXM radio. We sold that RV this year, and the SiriusXM was still playing. (I am sure that whoever ends up with that MH will believe we are unwittingly paying for the service.)
I bought a new F-150 this year with a 6 month subscription that expires 12/1/17. We turned it on to be sure it worked. In a couple of years, I will turn it on to see if it is still live.