Most ETA certifications are good for four years, and are maintained yearly. This means that while the certification is on a four-year cycle, it is maintained by yearly maintenance to stay up-to-date. Under ISO 17024, which ETA follows for certification bodies, professionals must stay up-to-date with their skills for their credentials to stay valid. You wouldn't want someone to work on your project who got certified 30 years ago and never worked in that field nor touched any of the technology! You can find how long your specific certification is good for under the Certifications menu. See the information box next to the certification description.