It is possible to lose trademark rights by failing to enforce them. Failure to enforce trademark rights does not automatically invalidate the trademark. but allowing infringing uses can dilute the distinctiveness of a trademark or lead to it becoming generic. To remain viable as a trademark, it must operate to distinguish a product or service from one source from identical, similar or related goods and services from a different source. If you allow your trademark to be used on competing goods or services, it may cease to operate as an identifier of your product or service that distinguishes it from those from another source. If a trademark no longer meets the criteria for a valid trademark, including distinctiveness and unlikelihood of confusion, then it will no longer be an enforceable trademark.
Failing to enforce trademark rights can result in other kinds of legal disadvantages, too. If you wait too long to file, an applicable statute of limitations may bar the claim. Even if the statute of limitations has not expired yet, a claim might be time-barred by the equitable doctrine of laches . And regardless of the timeframe, failing to object to infringement reasonably promptly after learning of it will put a trademark owner at risk of being barred from proceeding with a claim by an application of the equitable defenses of waiver or acquiescence.