The current easyCBM norms were developed in November 2016. Norms tend not to change too drastically over time. For instance, if you examine the Hasbrouck and Tindal ORF norms (Hasbrouck and Tindal ORF Norms), you will see that ORF norms have remained fairly constant over the past 25 years.
However, it is generally accepted that student demographics shift over time, as do classroom teaching practices. Thus, most test developers update their norms every 5-10 years.
Here at the University of Oregon, we opted to follow industry best practice in adopting a five-year norming cycle for the easyCBM assessments. We will be updating the Norms (and thus, the percentile tables) this year (2019) — analyzing results and then updating online during winter and early summer, respectively.