An associate pinged me with this question the other day and I really had no idea. My first thought was that they didn’t expire, since I didn’t actually receive a certificate after becoming certified; instead, just an email reporting that I passed the exam, my score, and the instructor’s congratulations. Nothing about when to retake the exam or when my certification expires.
My first thought of who to ask about this was the Sitecore community on Slack. At first I received my mixed answers, but someone provided an accurate answer: every 3 years. This seemed kind of vague for me, so I decided to get an official answer. I ended up emailing back my instructor (after almost 3 years!) and asking about when it expires, and I got an even better answer:
Certification expiration dates are the same as the Mainstream Support End Date for the corresponding Sitecore version per Sitecore Product Support Lifecycle policy. You can find the mainstream support end date for every version of Sitecore here: https://kb.sitecore.net/articles/641167
By checking the version of Sitecore I was trained on and its mainstream support end date, I was able to officially determine when my certification expires. However, you should make a point to get re-certified regularly as new versions of Sitecore come out with major changes. Hope this helps some of you out there!