Change occasionally to nightly.

NOTES

diff --git a/NOTES b/NOTES
index 593f1bc..0b4c241 100644
--- a/NOTES
+++ b/NOTES
@@ -6,7 +6,7 @@
 
 * Obtaining the source
 
-Tarballs will be posted occasionally at
+Tarballs will be posted nightly (but only when there are updates!) at
 
   http://pdos.lcs.mit.edu/~rsc/software/plan9