Lawn should get about 1" of water each week, irrigation and rain combined. Water heavy for a longer period or time rather than short, frequent every couple of hours rather than you would when you are first watering your new lawn. My schedule runs all zones for an hour three times a week.
1" per week is the general recommendation. It's also recommended to do 1 deep watering instead of several short watering cycles to get the 1" as this promotes deeper root growth for your grass.