How long does a trademark last in the United States?

In the United States common law trademark rights last as long as the mark is being used in commerce, possibly forever. If you have registered your trademark with the United States Patent and Trademark Office you must renew your registration every 10 years, provided the mark is constantly used. Failure to use a mark in commerce can cause the rights in the mark to be lost. During the fifth year of a registration and before the beginning of the sixth year a statement of use must be filed to continue the registration in force.

You should consult with an attorney that is familiar with trademark law to ensure that you are properly maintaining your trademarks.