grin--you think you want the session to never expire, but thats not what you really want is it--you want the session to continue until the browser closes, right?
Check your php.ini settings--
specifically:
session.cookie_lifetime :specifies the lifetime of the cookie in seconds which is sent to the browser. The value 0 means "until the browser is closed." Defaults to 0
also check:
session.use_only_cookies: specifies whether the module will only use cookies to store the session id on the client side. Defaults to 0 (disabled, for backward compatibility). Enabling this setting prevents attacks involved passing session ids in URLs. This setting was added in PHP 4.3.0.
And
session.use_cookies: specifies whether the module will use cookies to store the session id on the client side. Defaults to 1 (enabled).
Aww heck--just read up on sessions in the manual--there are a ton of ways things could be set up--