if (!defined('SESSION_TIMEOUT')) define('SESSION_TIMEOUT',1800);
The fix was simple, just change 1800 for whatever timeout (in seconds) you wish to have with the phpList admin session.
Seems like an easy fix right?
Well, it isn’t because it is recommending that you modify a core file which would most probably be overwritten with the next update so that’s not a permanent solution and it is a very bad one if you ask me.
So how do we fix that you might ask?
Well, you can define pretty much any of the default variables right from config.php and since this file contains the custom configuration it will never be overwritten by the updates.
So the solution would be pretty much to add the following line to your config/config.php:
Doing so you will override the value set in admin/init.php and the modification will stick throughout updates and upgrades.