A common question is how long do patents last?
In the U.S., utility patents and plant patents are valid for 20 years after their filing date. (This slightly longer change in duration came about in June 1995. Utility patents filed before that date are valid for 17 years from their issue date.) As for the third type of patent, a design patent, this patent type is valid for 14 years from the date of issuance.
IMPORTANT NOTE: There are various patent “maintenance fees” imposed by the U.S. Patent and Trademark Office (USPTO) over the lifetime of a patent. And if those fees aren’t paid, a patent could prematurely expire.
You can get an idea of the USPTO patent maintenance fees, as of September 30, 2007, by visiting the following page at the official government USPTO Web site and scrolling down to the Patent Maintenance Fees section: http://www.uspto.gov/web/offices/ac/qs/ope/fee2007september30.htm