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I'm sorry, but I don't think we have a feature that would let you limit with timeframe. We only have the following:
Unique Submission: http://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form.
But I think you can use the unique question limit. You can target the email address field or the name field. Then for them to be able to submit on the next month, simply add the same field for them to fill. Then hide the previous field in the form. You have to do this every month. Well, that means you will have a 12 fields for the whole year and people can still submit to the form if they want to by simply using another name.