CI Session cookie expiry / cookie_lifetime

Hi InsiteFX.
Sorry, but I dont understand your reply?

"Cookies will not write if output has already been sent to the page."
I dont get what you mean here, as like I said the cookie updates on most page load when I navigate round the web app its only on a few pages that it doesn't, and this is all pre anything being sent to the browser...

"Cookies will not update unless there is a page refresh."
Again like I said, once I have found one of these pages, I can refresh / re-load the page (f5) as many times as I want and the cookie expiry datetime in the browser stays the same even though in a pre-controller hook I update the session with new data which (from my understanding) should send an updated cookie to the browser with a new expiry datetime ...

Hope this clarifies the problem.

Many thanks,
Ben