PEP 387: Suggest waiting 5 years before removing a deprecated feature (#4156)

Author: brettcannon

peps/pep-0387.rst

@@ -169,10 +169,11 @@ several releases:
 
 3. Wait for the warning to appear in at least two minor Python
    versions of the same major version, or one minor version in an older
-   major version (e.g. for a warning in Python 3.10.0, you either wait
-   until at least Python 3.12 or Python 4.0 to make the change).
-
-   It's fine to wait more than two releases, for example:
+   major version (e.g., for a warning in Python 3.10.0, you either wait
+   until at least Python 3.12 or Python 4.0 to make the change). It is
+   preferred, though, to wait 5 years before removal (e.g., warn starting in
+   Python 3.10, removal in 3.15; this happens to coincide with the current
+   lifetime of a minor release of Python).
 
    - If the expected maintenance overhead and security risk of the
      deprecated behavior is small (e.g. an old function is reimplemented