Does nexplanon birthcontrol start to loose effectiveness before the 3 years?

Nexplanon: As with many medications, manufacturers place expiration dates on their use which are in many cases underestimates of effectiveness, but "three years" may in some instances not be protective contraception. Ovulation may occur with insufficient effect by the progestin in Nexplanon to prevent implantation of the fertilized egg, so use other birth control to avoid this possibility.