If it doesn't hold 12.6 volts when fully charged is all you can do, or take it somewhere with a proper drop tester which measures the voltage decay under load.
You need to accept some degradation though, if you measure yoiur battery now and it's 12.4V there isn't necessarily anything wrong with it.
12.4V is acceptable. Mine sags to 12.3V overnight, but only sags to 12.1V after a week of doing nothing.
Because a lot of people seem to keep their Alfas for the weekend, or as a second car, then the batteries get hell because the worst thing you can do for a lead acid battery is to store it partially discharged. (or when it discharges below 90% SOC, fail to put it even onto a trickle charge)
Newer technology (for comparison), most lithium cells for example, should be stored and transported half discharged.
I always start with the lights on (Don't know why the headlamps would blow, but someone must have started that off for a reason). Even when it's freezing I don't get any trouble. BUT I use the car every day and it almost always gets a long enough run to at least fully recharge the battery between starts.
HHmmmm...I do also do connector maintenance, I reseat all connectors in any area I'm working on just out of habit. You can improve the quality of a lot of connections in one go just by doing that