How do you get the best longevity from automatic headlight, by turning them off during the day while drive (legal in NJ) or by leaving them on always? In other words does switching them off everyday lessen or increase the longevity of a headlamp, low beam on a 03 Chevy Trail Blazer LT.

Switching them off everday would increase the longevity of the headlamps.

Thanks

... but decreases the safety factor in everyday driving.
Have you noticed the amount of drivers on the road today who just don't see you (like driving drunk) and you're in plain view?
All because their cellphone conversation is much more important than their driving.

How often do you have to replace a headlamp. Two cars, both 10 yrs old. The dome, lic plate and a brake/tail lamp. Headlamps and DRL's still going strong.

And we are assuming that the headlights are not HD Xenon lamps, nor the tail lamps are LED's. Xenon lamps have no filament and neither do LEDS. Their intensity degrades over tiime.