How and when to check the status of an In-app Subscriptions?

Question

Android

When purchasing a subscription, the application receives a token and product id from Google Play, sends it to the server for server-side validation. I check the token on the server and activate the subscription for the selected period. The question is what to do when the paid period ends? At what point should you check if the subscription has been renewed, and how to do it, because (theoretically) the token should change? Something the doc is silent about it.