This is because session.gc_maxlifetime is used now, and it's set to a low 24 min by default, mening you'll constantly have to login again if you tend to do other stuff then just browsing around your site all the time.

Suggestion would be to do something like this in php session handler:

ini_set("session.gc_maxlifetime", $ini->variable('Session', 'SessionTimeout') );

This means session will last for 3 days with default settings, just like with DB handler.