CheckSession call and SSO into SPA with cookies

Doubts i had are as follows,

  1. What is the need of check session calls in auth0 SPA applications - for example i made an application which would fetch the user profile information and store it in local storage is there an necessity to perform check session call for every 10 minutes interval ?
  2. I have two SPA applications how to do SSO into another application from application 1 and if application 1 is logged out by the user still application 2 should remain logged in.