Ive never purchased a complete BCM rifle or upper, but I've been solely using BCM parts for my last 5 builds. My first BCM build is in the 3500rd range, has never had more than a barrel swab and spray down. Not a single fail to fire, feed issue, or short stroke.
IRRC it was BCM that performed a 10k rd torture test (no cleaning) on one of their rifles which had no major malfunctions.