I’m not sure what year it implemented headlights turning off with the ignition but given it’s Volvo I suspect quite early. I’ve always run my car with the headlights on. Even if I had daytime running lights I’d run with my headlights on. Because why not?
Over the weekend I had a headlight go out. Always thinking, I decided to run the parking lights instead. Not thinking, I didn’t turn them off when I parked it Saturday.
This morning the battery was dead-dead. Not-a-click dead. A boost from a neighbor and 2 hours later I’m good to go. An idling car is not an efficient battery charger but it’s efficient enough.