Added for 2.15.
Just to be clear again: the information in previous post still applies.
Moreover, I would image cookies mostly would be used for login on "Other" type. All basic supported blogs / forums already have ability to save user. So for all normal type just use that and it will login before leeching.
Also all websites usually add a lot of random cookies. For "Other" type login information in cookies is usually stored in one / two cookies.
For example:
https://softarchive.netFor login you need only: "id" and "hash" cookies.
Cookies does not last forever, if it's login make sure to mark in websites "Remember me" option and not logout from website (because that would also invalidate cookies). They can last a year or just a month. It solely depends on website.
In program you only need "Name", "Value" and specify some expiration date.
Attaching screenshot of Firefox cookies window. "Content" is the "Value".