Well, i lost battery with my Bose X once with doors off in a chooper. It's not nice, i agree, but you are definetly still able to communicate......
Also the Bose starts cutting out for splittseconds for at least 1-2 hours before the Batteries go completly dead, means you have enough time to change the batteries before ANR goes completly, you will just have short cutouts every 5 minutes.
Like S88 said, if u buy it you will never look back!