You can disavow your question which means it will become anonymous and you will no longer receive notifications for the question, even if someone leaves a comment. To do this, just go to your questions page and click the broken link symbol. It will ask you if you want to disavow the question, then click 'yes.'
Disavow your question. Go to your profile, click on 'question' and you will find the disavow button on the bottom right of every question. Disavowing is the same as 'closing' your question. Your question will still be there but you won't receive notifications on it.
I was actually wondering about this, that if the asker no longer needs any more opinions, a question should be lockable. You cannot do that yet, but I think it is a decent feature request to @GirlsAskGuys.
Go to your overview of questions, then click the little chain icon. This unlinks the question from your account. You will become anonymous in your question (if you weren't already) and you will no longer receive any notifications of it.