Normal halogen bulbs will dim with use Luke, the heat turns the glass envelops black from the inside. Have a look at this :
Middle pair of beams are the LED bulbs, on the left new Chinabay "Xenon-look" halogens, on the right, a few-month-old Nightbreakers.
As you can see, the LEDs are the brightest with the best beam pattern.
https://www.classiccarleds.co.uk/col...nversion-9-32v
If you really want to see what they're like on a Volvo, i can get pics tonight but aside from the background, they won't be much different. However, here's a dash-cam vid from my Volvo which shows the beam pattern. There's also a lunatic in a Ford overtaking on a narrow, very bumpy road with anoncoming car and not much room at about 9:10 give or take a few seconds
https://youtu.be/RDwk_SLSaDk
Enjoy!
