How long should battery minder take, in conditioning mode?

You probably already know this, but blinking is good -- it means the charger is in "desulphate" mode. I think it gives the battery little pulses that keep the sulphur from sticking to the plates. If there were a constant charge without the pulses, the sulphur would build up. I don't really know the technical details of how this works, but it sure does -- my batteries are lasting much longer than they used to, before I got a BatteryMinder Plus.