Back in late 2015 I replaced the original battery in the G as part of preventive maintenance. Car still started (albeit cranked slightly slower in the winter). Since then the battery has been used in the garage (unheated) periodically as a 12V source. I keep it on a battery tender when not in use.

Given the battery is almost a decade old I brought it a local shop to get tested.



Surprisingly it's still good. No G anymore to test for cranking, but it did fire up the accord just fine.

 

This was the key to your battery's long life.

 

What kills these batteries is the IPDM programming. There is documentation in the FSM about "battery saving" features that usually affect owners who have done updates. Has the alternator toggling charges while vehicle is on since 14v is not needed all the time.
Usually follows a slow crank after a couple of days of use. When you remove the battery from the vehicle and proceed to follow battery maintaining practices it will give you the expected life intended.

 

The honda has something like that. When driving under some conditions - daytime, low electrical demand (headlights, seat heaters off, low fan speed, etc.), the alternator barely puts anything out, <13V according to the volt meter in the cig plug (not exactly true batt voltage due to losses but still an indicator). Doesn't do much to recharge the battery if the car is driven occasionally. This ultimately leads to premature battery death.

Which battery maintaining practices are you referring to? I often had the G hooked up to the battery tender because the car was used occasionally. I never removed the battery. Occasionally I'd pop the caps and check water level.

 

The honda has something like that. When driving under some conditions - daytime, low electrical demand (headlights, seat heaters off, low fan speed, etc.), the alternator barely puts anything out, <13V according to the volt meter in the cig plug (not exactly true batt voltage due to losses but still an indicator). Doesn't do much to recharge the battery if the car is driven occasionally. This ultimately leads to premature battery death.

Which battery maintaining practices are you referring to? I often had the G hooked up to the battery tender because the car was used occasionally. I never removed the battery. Occasionally I'd pop the caps and check water level.

Store in a ventilated, not so humid area with connected to a tender when not in use and make sure you do use the damn thing. Pretty much what you have been doing.
Confirming the G is the culprit for battery drains and not batteries themselves