NEWS: Add news about cache expiry
diff --git a/NEWS b/NEWS
index 41598db..7aa0044 100644
--- a/NEWS
+++ b/NEWS
@@ -20,6 +20,9 @@
 
   o BuildStream now requires python version >= 3.5
   o Added new `bst init` command to initialize a new project.
+  o BuildStream will now automatically clean up old artifacts when it
+    runs out of space. The exact behavior is configurable in
+    `userconf.yaml`.
 
   o Cross junction tracking is now disabled by default for projects
     which can support this by using project.refs ref-storage