Basically, it would be up to the asker to regain the right to ask: by answering a few questions and getting a couple of upvotes, the right is back again (at least, based on the current options out there). I don't understand what would change after 6 to 8 weeks of ban. A bad asker would be back asking bad questions.
I'm not even saying that I know what defines a bad question nor that banning itself is the right choice, but if the action is taken, in my opinion the best strategy would be to try to force a change in the attitude
Update: AS I said above, I don't have a position taken on whether ANY action should be taken with respect to bad questions. What I do believe is that IF somebody is declared persona non grata due to the low quality of the questions, that person will still be unwelcomed three months later, unless something else changes. Of course, if any action is taken whatsoever, SE should send a few warnings to the user in advance to try to improve the behavior before the ban. If the user persists even after the warnings, what makes you think that behavior won't be the same after three months? Giving the user the option to gain some rep might promote a better behavior in a very positive way. In fact, inducing the user to answer should teach her/him how to read the documentation, how to do web searches and even how to find duplicate questions in SE itself. I never proposed a minimum answer/question ratio nor any other kind of limit, I am only replying to the very specific question: "Can bad question askers be forgiven?".