JSolo
2500 Posts Club!
I sold the accord with a 9 yr old battery out of my G37 (original battery from late 2011). Around year 4 in that battery's life, it was removed from service and used as a 12V source in the garage. Charge kept up by an even older battery tender (1.25A). About the only time the tender got disconnected was when I needed to move something and the wires were in the way (rare). Few months before selling the accord I replaced the battery with one from costco. To supplement the payout from carmax, I decided to return the new battery and in its place installed the one from the garage. Car started fine each time. Few weeks prior, I had pepboys test that battery. Their tool said it was still good for ~500cca, rated around 650 when new.
tl;dr keep the battey tenderized when not in use.
tl;dr keep the battey tenderized when not in use.