when you are going to require someone to pay for your app every year for the rest of their lives you should put that on your sales page in the play store so that before even attempting to download the app one will stop if they don't want to have to subscribe and pay yearly, or monthly or whatever for the rest of life... make an app that works without a subscription and it would be reasonable but paying for the app every year or month for the rest of your life is unreasonable and greed