From time to time, we ignore our own policy (#3475)

diff --git a/docs/api-stability.rst b/docs/api-stability.rst
index 53669b0..7ba1d42 100644
--- a/docs/api-stability.rst
+++ b/docs/api-stability.rst
@@ -49,3 +49,7 @@
 
 In short, code that runs without warnings will always continue to work for a
 period of two releases.
+
+From time to time, we may decide to deprecate an API that is particularly
+widely used. In these cases, we may decide to provide an extended deprecation
+period, at our discretion.