I began using the Concord RG batteries about 6 years ago.
Like, Ron, I used to change batteries every 3 years.
After I purchased my most recent Concord RG battery, I removed the "old" RG and then discharged it.
When I say discharged, I mean that I connected a bulb to the battery and let it run down.
A few days later, when I returned to the hanger, I connected the discharged battery to my charger and recharged the RG battery.
I then check the voltage every few months. After one year of no use, other than voltage checking, I find there is no loss of voltage.
Granted, I should reinstall it in the airplane and see what happens. This will happen in September when I do the annual.
I am saying that I hope to be able to use the two RG batteries over and over.