RCW 19.108.060 imposes a three-year period running from discovery or from the date the misappropriation should have been discovered through reasonable diligence. Two features deserve attention.
The discovery rule is built in. Unlike many statutes of limitation, the accrual standard is stated on the face of the Act.
Continuing misappropriation is a single claim. The second sentence forecloses the argument that each successive use restarts the clock. This is the standard UTSA formulation and it functions as a repose mechanism for defendants whose use has been ongoing and known.