I was quite surprised today when I saw the message telling me that I can no longer post questions because of the 50 questions limit. So I think it would be nice if users were informed earlier that they are going to be blocked from asking questions.
Maybe there could be message at 30 questions? For example:
Note: you have asked 30 of your 50 monthly questions. Once you reach the limit of 50 per month, you will have to wait before asking more questions.
Then the same message at 40, 45, etc.