AWS cognito: In mobile app how to set token expiry to infinite

Im using cognito developer authentication provider as my access control for my mobile app. Problem is in mobile apps, once the user logs in he/she doesnt have to login again. But with AWS cognito the token only lasts some 1 hour or so. How can I make sure the token expiry is set to infinite maybe 1 year or so. Please advice

thanks, Rajan