Lwiddis wrote:
"Since it seems obvious to you, how often do you think I should replace my batteries? Every 3? 4? 5? 6? 7? years. Or does the longevity depend on conditions of use, depth of use, frequency of use, temperature or other factors."
What's a good night's sleep for your spouse worth....couple of more months before you replace 7 year old batteries? Some call me "thrifty" but being pennywise here isn't what I'd do.
If you're going to change the batteries as a time change item wouldn't you want to go with the MIL spec for AGM batteries which is generally 24 months?
Having been involved in field testing of batteries for years, I haven't seen where AGM batteries have a habit of suddenly failing based on a set age. The tend to degrade predictably based on temperature, age, average state of charge, charge cycles etc. If the battery capacity and load tests good today, the degradation over time from this point on should be fairly predictable.