We will need more info, halogen or Hid headlamps?
If halogen there are many uopgrade bulbs out there, I found none of them seem to last not even the expensive ones.
If HId then just new cheap bulds seem to work well on my D3, Iirc they were 12 quid the pair.
If plastic lens, then a good polish is also worth the effort, as they oxidise restricting the amount of light that can pass.