Under United States law, trademarks and service marks can potentially last indefinitely. However, certain contitions much be met:
- Use in commerce. The trademark holder must continue to offer the goods or services covered by the trademark or service mark in commerce. If they stop using the mark, then after a certain time, the mark expires. For Federally registered marks, they must be in use in interstate commerce, or after over three years, they will expire.
- Paying maintenance fees: Trademarks registered at the state, fFederal or international level do require payment of a maintenance fee periodically. The period and amound vary by the agency involved.
- Defense of the trademark: If another party deliberately and persistently infringes on the trademark, and the trademark holder does nothing about it, a court may rule that the trademark has been forfeited. Minor or accidental infringements do not have this effect, and defending the mark may be as simple as writing a leeter to the offending party askint them to stop.
- Trademarks vs. generic terms: If a trademark becomes so identiffied in the public mind with a product or service that it ceases to identify its source, then the trademark beccomes a generic term and loses its trademark statuus. See the box at right for a list of familiar terms which started out as trademarks, but have generic. A trademark holder may help protect the tradmark status be always using it as an adjective, rather than as a noun or verb, or by always using the appropriate tradmark or service mark symbol. Example: Sheetrock brand gypsum wallboard or Kleenex brand facial tissues.