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 0ce47e8..844ec51 100644
--- a/BRANCHES.md
+++ b/BRANCHES.md
@@ -24,7 +24,7 @@
 ABI compatibility within LTS branches; see the next section for details.
 
 New LTS branches are usually created around the time of a new major version.
-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