Update BRANCHES.md

Co-authored-by: Dave Rodgman <dave.rodgman@arm.com>
Signed-off-by: Janos Follath <janos.follath@arm.com>
diff --git a/BRANCHES.md b/BRANCHES.md
index 8f2c8fc..6d2e5c0 100644
--- a/BRANCHES.md
+++ b/BRANCHES.md
@@ -19,7 +19,7 @@
 Every major version will become an LTS branch when the next major version is
 released. We may occasionally create LTS branches from other releases at our
 discretion.
-After a new LTS branch is created, it remains supported for at least 3 years.
+When a new LTS branch is created, it usually remains supported for three years.
 
 ## Backwards Compatibility for application code