sessions expiring

I can't find the proper settings to keep unattended sessions from expiring in about an hour. Specifically, the $_SESSION variable contents disappear. I've read the docs, but nothing seems to work. Any ideas? Here are the session parameters that are in effect:

session.auto_start    On
session.bug_compat_42    On
session.bug_compat_warn    On
session.cache_expire    180
session.cache_limiter    nocache
session.cookie_domain    no value
session.cookie_lifetime    0
session.cookie_path    /
session.cookie_secure    Off
session.entropy_file    no value
session.entropy_length    0
session.gc_divisor    100
session.gc_maxlifetime    28800
session.gc_probability    0
session.name    PHPSESSID
session.referer_check    no value
session.save_handler    files
session.save_path    /var/lib/php4
session.serialize_handler    php
session.use_cookies    On
session.use_only_cookies    Off
session.use_trans_sid    Off

Thanks. John Gunther Bucks vs Bytes Inc