Give you all something to think about...
Don't believe the eye(s) on your batteries... Do the proper testing by load testing and using hydrometer... My batteries in my 2002 Dodge Cummins pickup are the orignal batteries from the dealer that are going on 9 years old. The little eyes have been black now for over 1 year but the batteries continue to pass the load test without any issues.
Also keeping the batteries clean and the terminals clean make a huge difference in a life span of a battery. Even week when I wash the truck I wash the engine bay out including the batteries. Then afterwards I coat the terminal in a light coat of engine oil to protect them.
Then if I start the truck I never short trip it. Being diesel engine require a huge amount of AMPs to start I make sure to drive it at least 5-10 miles before shutting down. This insures the batteries are charged up again for the next start.