In the interim you can update:
 
/core/ServiceProviders/MinphpBridge.php
	At the bottom of the file is a set of TTLs:
 
$ttls = [
    'ttl' => 1800, // 30 mins
    'cookie_ttl' => 604800, // 7 days
];
	Change the 'ttl' value to the number of seconds a session should last, e.g.:
 
$ttls = [
    'ttl' => 14400, // 4 hours
    'cookie_ttl' => 604800, // 7 days
];
	Making these configurable from the config file should occur in v4.2.