My 2012 ML headlights and dipped lights seem to be much dimer than before... Any ide why this should be happening?

[Flyinspanner]

If you have Xenons, the supply voltage is 20-30 THOUSAND volts

LED 12v lamps would explode.

lamps do degrade over time, just replace with new ones of the correct (same) type.
If they are halogen, the Osram Nightbreakers are a suitable upgrade.

 

[tombell]

Halfords changed the dipped and main beam bulbs for Halogen HAL ADV 5000K +50 H7 477 (£73.00) but lights don't seem any better.

I noticed coming home in the dark tonight that the dipped beam only shines about 25 yards ahead so I guess I'll have to get them adjusted to about 100 yard?