If you are referring to halogen headlamp bulbs dimming with age, it is either a feature or a benefit

according to autozone.com anyway

Halogen replacement bulb, with basic performance, from the leading supplier of automotive lighting.

Legal for on road use

OE quality

Headlights dim over time

Replace headlights in pairs

Usually because of a lower voltage.... either dying battery or a bad voltage regulator or alternator.

they should not really give less light with the time, but they get dirty. As well as the plastic pieces of your tail/front/side lights.

I'm guessing the filament or coil attenuates...