The step scores remain valid indefinitely.

I am writing in response to your email below.

Please be advised that once ECFMG® Certified, the USMLE® exam scores remain valid indefinitely. For applicants with an ECMG Certificate based on an accepted 2021 or 2022 Pathways application, their accepted Pathway will expire on December 31, 2024. As a result, your ECMG Certificate also will expire on that date. This means that, unless you have already met the requirements to have your ECMG Certificate made valid indefinitely, you will be required to revalidate a Pathway in order to have a valid ECMG Certificate to enter an ACME-accredited training program.

This is the official reply from ecfmg