The "monopoly" granted by a patent is subject to set term of years, after which time the subject matter of your patent enters the public domain for anyone to use. The years you're allotted depends on the type of patent.

Design patents are granted for a 14-year life. Utility patents filed after June 7, 1995 last for 20 years from the date of application, or 17 years from the date of issuance of the patent, whichever is longer.

The duration of a patent can be extended if any of the following types of delays occur:

Regulatory Review - Patents may be extended if marketing has been delayed due to regulatory review.

Failure of the PTO to examine a new application - If the PTO fails to examine a new application within 14 months of filing, the term can be extended.

Failure of the PTO office to issue a patent within 3 years - This exception only applies if the applicant didn't cause the delay.

Failure of the PTO to undertake certain administrative actions - An extension will be granted if the PTO fails to undertake certain action necessary to grant the patent for more than four months.

Pendency Period and Termination of Patent Rights

The time between the date that a patent is filed and the patent is issued is called the pendency period. As an applicant, you have no rights under patent law during this period to stop anyone from using or marketing your idea. However, once the patent issues, you have the right to sue to stop any infringing activity. You may also be entitled to seek royalties for the period subsequent to publication.

Patents are non-renewable. Once they expire, you can't re-patent the same idea. In exchange for the monopoly previously enjoyed, the new technology becomes part of the public domain. It's intended to become a building block for even more advanced technological advancements, which may in turn be the subject of future patents.