title: SKPaymentQueue: What happens if I never call finishTransaction:?
body: <p>My app will allow the user upgrade to Pro features via an In-App Purchase. I am validating the receipt data with my own server, and one the confirmation comes back from my server, I call finishTransaction:</p>
  
  <p>What will happen if the validation fails (perhaps not due to piracy attempt) and I dont call finishTransaction: ? Will it stay in the queue indefinitely? </p>