Red Points briefly outlines how long a trademark lasts in the United States, and what to do when that time runs out.
A federal trademark lasts 10 years from the date of registration, with 10-year renewal terms. Between the fifth and sixth year after the registration date, the registrant must file an affidavit to state that the mark is still in use. It’s important for the registrant to keep this date in mind, as the registration is cancelled if no affidavit is filed. The registrant must personally remember to do so, as no reminder is sent from the USPTO.
A trademark registration may remain in force for potentially unlimited consecutive ten-year periods, as long as the owner meets the legal requirements for post-registration maintenance and renewal, while filing all necessary documents on time.
If a trademark becomes expired or canceled, the trademark still has "common law rights" that can be applied. This enables the law user to challenge another party’s use of their own trademark in court.
If you’d like to read further about trademarks, you can find out more on the USPTO’s website here.