Ok, here's what I know. Before I edited session.cookie_lifetime, I had to re-login every time I visited my php forum. Once I set the value to the same that was in my config.inc.php, I didn't have to relogin until a few days passed (the default lifetime was 1036800 seconds btw). Once I changed that value to 31536000 (both in config.inc.php and in the php.ini file) I haven't had to relogin once.
I didn't make any other changes to either the forum itself or the php.ini file. And it recognizes me each time. So if I am wrong here, don't tell my server. At least it believes me and is working the way I think it should []/w3timages/icons/smile.gif[/]