sess_expire_on_close config option questions

[eluser]besson3c[/eluser]
I'm trying to implement a "save password" checkbox in my login form. I would like for users that have this option checked for this config option to be set as false, and for users that don't for this config option to be set true.

It appears that a simple $this->config->set_item('sess_expire_on_close', true) does not work to modify the value of "false" entered into my config file, I'm assuming because the session has already been initialized and the cookie already created.

What is the most elegant way to recreate session information depending on this checkbox selection, or, IOW, how can "sess_expire_on_close" be set dynamically?