Change the EE session lifepsan time

functions.php

<?php //Please do not ad the opening PHP tag if you already have one.

function tw_ee_change_session_lifespan() {
  // Set the value here to be the number of minutes you want the sesssion to be
  // EE uses 60 buy default (1 hour) but here we change it to 15. Simply use another value for that lenth of time so,
  // 15 = 15 minutes, 30 = 30 minutes etc
  $minutes = 15;
  
  //Return the number of minutes in seconds as that is what is used by PHP.
  return $minutes * MINUTE_IN_SECONDS;
}
add_filter( 'FHEE__EE_Session__construct___lifespan', 'tw_ee_change_session_lifespan');