I bought a nexus 7 in 2012 and it came with a $20.00 gift card. When I went to install apps from the app store, it asked me to sign into my google account. I signed into my gmail account and received the $20.00 for the play store. I purchased one or two items but I'm positive I still have a good $15.00 left. Where do I go to check how much google play store money I have left on my account? I went to wallet.google.com and it asked me to create a payment method, but I know for a fact that I still ahve a good $15.00 left on that gift card... Do the gift cards expire?