Until a couple of years ago I had two domestic batteries and 70 watts of solar panel. Overnight my domestic battery voltage used to fall to below 12.0 volts every night. Since uprating my panels to 125 Watts and adding the starter battery to the domestic bank the voltage is usually at about 12.2 or 12.3 first thing in the morning. All three batteries appear to be in good condition, they hold their charge well and are normally used to start the engine.
At a conservative estimate two of these batteries have been discharged by 40% or more around 600 times. The bank of three has been discharged by more than 20% more than 200 times, so two have accumulated 800+ cycles.