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``As to your question, there is no set answer. No federal rule or regulation sets the time length for examination of patent applications. Depending on the ``art unit`` or technology area, an application can sit between one and three years before it is first examined. Very few applications are allowed following the first examination. More often, the examiner rejects the claims. The applicant then argues that the prior art cited by the Examiner does not teach or suggest the invention claimed. The claims may also be amended. This back-and-forth with the patent office may take a year or more. If the applicant cannot convince the examiner, the applicant can appeal to the Patent Office board of appeals, a process which may take another three years.

I hope this is helpful. Let me know if you have any other questions.``