Have been pulling out my hair trying to find out why my sessions are being terminated/killed/destroyed at 30 minutes. Well it looks like Debian based systems have a special
This is a question for serverfault.com.
However, change session.gc_maxlifetime in /etc/php5/apache2/php.ini or - if you don't have an apache2 one - one of the other /etc/php5/*/php.ini files. The script /usr/lib/php5/maxlifetime will then use the maximum for that setting found in any of those files.
Editing maxlifetime won't help or at least only until the php5-common package is updated again.