I have a battery in a vehicle that is running low. It has not failed, but I measured the voltage, and so I know it's running low (11.6V). From what I've read, a 12V battery should really be well over 12V.
I bought a new battery, and placed it in the vehicle (not connected), with the necessary tools and supplies to perform the replacement.
I'm not concerned about the inconvenience or safety of having to replace the old battery when it finally fails.
The vehicle requires some body work, which is scheduled in about a month, and will take 5-8 days. Although I can ask, I cannot force the body shop to disconnect/reconnect the battery each time they keep doors/trunk open for an extended period of time.
My thinking is to wait until the old battery fails to replace it, up to a maximum of 6 months. I'm thinking 6 months, because I don't want the new battery to run low without being charged (the new battery is currently at 12.78V). I do not have access to a battery charger.
Does my plan sound good? My goal is to maximize the life of the new battery, so that I minimize the environmental and financial impact of using the vehicle. I also don't want the new battery to get damaged (by getting drained) when the vehicle is having body work performed.