I am not really in favour of turning it off because some newcomers may not check it and maybe expecting an e-mail. The good thing about it is if you do check your e-mail is on a regular basis, you will know when somebody replies to your post.
You will also be informed about older posts that you probably don't check any more. You have to remember that people searched the older threads and may have something to say, if we never checked them, some people might not get the help they need. If you don't wish to receive e-mails to every reply, just uncheck your box before you post.