Why do certifications expire?

Certifications expire because the thing they certify doesn't stay true forever. Skills fade and standards evolve (professional certs), equipment drifts out of calibration (technical certs), organizations change processes and people (ISO and quality certs), and cryptographic keys become riskier the longer they live (SSL/TLS certs). An expiry date forces a periodic re-check that the certified claim still holds.

There's also an accountability motive: recurring renewal keeps practitioners current with continuing-education requirements and keeps companies re-auditable, and yes — it also funds the certifying bodies.

Whatever the reason, the practical consequence is the same: every certification you hold is a deadline you own. Listing them all with renewal dates and lead times in one place is the difference between planned renewals and panicked ones.