I believe it goes something like this …
When you "Accept Cookies", the system installs a range of cookies on your machine. [*] … One of these is a flag that tells the server that you have accepted.
According to the setting of that flag; you will see either; (a) the "keep me logged-in" checkbox, or (b) the banner inviting you to accept cookies.
[Curiously though; I have noticed that some subsidiary pages continue to show the banner.]
To "change your mind" the safest thing would be to remove all cookies from the machine.
MichaelG.
[*] The range of cookies could be quite wide, but will mostly be to do with tracking behaviour … for the benefit of [and the billing of] the "sponsoring" Advertisers.