"Batteries are a wear item, typically should be able to get 8-10 yrs then replace them."
I used to sell a lot of batteries {starting and deep cycle} as the marine chandlery I worked in was a Trojan dealer. The Trojan rep assured me that the planned obsolescence of any battery is 3 years... yes lots of folks do better depending on use and maintenance not to mention weather {our southern Arizona sun can kill just about any battery in 3 years or less.
When the local auto shop sells you a 5, 7 or more year battery that is the same 3 year battery sitting next to it on the shelf but just with a much higher price. Battery manufacturers know that the average owner of a vehicle turns it every 3 - 5 years and chances are they will never have to prorate much less replace it. At three years I start watching it closely and know that before 5 it will need to be replaced.
Some folks keep tires for 8 - 10 years but in both cases you are inviting a problem and Mr. Murphy is not your friend.
As always... Opinions and YMMV.
:C