Polish

See gh-29955

spring-web/src/main/java/org/springframework/http/CacheControl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -326,6 +326,8 @@ public class CacheControl {
 	 * Add an "immutable" directive.
 	 * <p>This directive indicates that the origin server will not update the
 	 * representation of that resource during the freshness lifetime of the response.
+	 * Adding a {@link #maxAge(Duration) max-age} directive is strongly advised
+	 * to enforce the actual freshness lifetime.
 	 * @return {@code this}, to facilitate method chaining
 	 * @see <a href="https://tools.ietf.org/html/rfc8246">rfc8246</a>
 	 */