Persistant cookie goes away....

I can successfully set the persistant cookie using RedirectFromLoginPage. I can close the browser and reopen it and yes, it uses the cookie.

But the cookie seems to still expire after the timeout period (default of 20 minutes). Why is this and how can I fix this?

Thanks in advance!

Ok the cookie stays there. But I am sent to the login page. So this line

If Context.User.Identity.IsAuthenticatedThen

is obviously telling me i'm not authenticated anymore. What am I missing?