I'd guess 30-35 minutes generally, up to 45 minutes if there's a problem. So, I'd leave by 7 at the latest, but probably 6:45 just to be safe. Also, are you hoping to be in parking by 7:30, or at the gate? Because if you want to be at the gate, add another 15-20 minutes for parking/riding tram/security check, putting your departure time back to 6:30 or so.