From Home Again's website:
If pet owners decide not to renew their annual membership, will their pets’ microchip ID codes and information still remain in the HomeAgain database?
Once entered in the HomeAgain database, microchips are registered for life, whether or not pet owners renew their annual memberships, and contact information may be updated online anytime free of charge by logging into HomeAgain.com. However, if a non-member’s pet is lost, they are not eligible for the value-added benefits included with the annual HomeAgain membership, such as proactive outreach to local PetRescuer volunteers, travel assistance for found pets, the 24/7 medical hotline, etc.
I used this tool to verify the information on Katie's microchip. It's good to periodically check.
Pet Microchip Lookup - Powered by AAHA AAHA Universal Microchip Lookup Tool | AAHA