12 Volt battery replacement on 1st gen 2011 to 2015 Chevy Volt

Everyone says to change the 12AGM battery after 5 or 6 years. I guess I didn't get the memo because this one is original, been in there since the car was made in 2011, so it's 15 years old and the weird codes just started popping up, and the engine running at high speeds and other strange issues directly associated with a weak 12 volt battery which runs the electronics.