I have a prepaid Alltell phone for emergency use etc. I don't turn it on much over the winter but more when I golf in the summer and am away from the home phone.
The Alltel system wiped out my auto replenish when thier computer went thru an update during a company merger. The result was my phone stopped working without any notice to me. By the time I caught it, they wiped out my built up minutes/$. I had to reactivate the auto replenish and then call them to get my minutes, $97 worth, put back in my balance.
SO HEADS UP.