CompTIA just released a new certification renewal policy that puts a 3 year shelf life on their certifications. This is a significant change for CompTIA.
You can read about it here:
CompTIA Certification Renewal Policy
Cert Shelf Life
You don't necessarily have to retake a certification exam to stay current but can earn continuing education credits to do so. This sounds similar to the CISSP certification.
Author: CompTIA Security+: Get Certified Get Ahead