How long can I keep Olaplex No.3 in my hair? Olaplex No.3 reaches its max efficacy at 30-45 minutes, however Olaplex is actively working in the hair as long as the hair remains moist. May 13, 2020 06:32 Updated Related articles What is the difference between Olaplex No. 1, No. 2 and No. 3? What are the growth ingredients in Olaplex No.5? What is the difference between Olaplex No.6 & No.7? Who is Olaplex for? How does Olaplex work?