It’s one and done.I didn't know that, they need to be renewed every 5 years? do they need to be removed/replaced or just renewed?
Once a car gets its sticker, then it is not renewable. Also, it is only 4 years.
Clean Air Vehicle Decals - California DMV
If you drive a vehicle that meets certain emissions standards and other criteria, you may be able to get Clean Air Vehicle (CAV) decals and a CAV decal identification (ID) card, which allow single occupancy use of High Occupancy Vehicle (HOV, or carpool) lanes.
www.dmv.ca.gov
If you get a blue (2021) sticker this year, it expires on 1/1/2025. The blue sticker (unless they extend) expires prior to the Sept. 30, 2025 end of single person carpool lane occupancy.