I understand basically create favicon and hang appropriate expire headers browser will cache it and prevent asking for it.

My real question is how do you stop browser asking for favicon when there's no icon apply for a restricted time (i.e. thirty days)?

You can't stop anybody from coming to a demands. You are able to only decide what related to the demands you obtain.

Nothing you need to do stop me from opening an association to port 80 in your server and requesting the favicon.

But when you're just speaking about regular folk on common browsers, you need to just give Them a favicon so that they stop asking. Create a whitened square or something like that, does not matter.