Esri Web Application Developer certification expire after some period of time? If so, how long?
Certifications don't expire, but they are developed for a certain version of the software. And since the software evolves, a certification passed for a certain version may not be really meaningful anymore after a time. Esri doesn't develop certifications for every new version but rather when they judge that the changes between versions are significant enough for the certification to be revised. And for a given version, a review of the certification might be relevant for a certain product/certification type, but not for the other.
----- Update - 11 March 2018 -----
See the Esri Certificate Verification page for reference:
As the technical certification program continues to grow, changes and improvements are made to ensure Esri offers the best possible Certification Exams to the global ArcGIS community. An exam will be updated only if more than 10 percent of its content is impacted by software version changes. Exams that are minimally impacted (less than 10 percent) will not be updated for the new software version. If we decide not to update a particular exam, it means that exam applies to the latest release of the software. [...]
Esri certification exams are retired in accordance with the Esri Product Life Cycle Support Policy for mature support. Exam retirement does not affect any certifications that have been issued for that version. All existing certifications will remain active.
Esri plans to re-think its certification system so that it's calendar-based and not version-based anymore. As per today, the change is not yet visible in the available exams.
See this blog post - The Future of Exam Development for details.
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