diff --git a/book/source/adv/certificates.md b/book/source/adv/certificates.md
index 1cf09e7..cbf5cfa 100644
--- a/book/source/adv/certificates.md
+++ b/book/source/adv/certificates.md
@@ -21,6 +21,8 @@ In this chapter, we aim to delve deeper into the advanced concepts surrounding O
 
 ## Certificate validity and expiration
 
+Maintaining the validity of OpenPGP certificates is essential for the security and reliability of cryptographic communications. Expiration dates play a key role in this process, acting as a built-in check that prompts users to review and renew their certificates periodically.
+
 Certificates are composites of components that are linked together using [signatures](../signing_components).
 
 A certificate can be valid or invalid as a whole. However, even when a certificate is valid, individual components (subkeys or identities) of it can be invalid.