Xenon bulb query for my TT

[Jimbo's TT]

Hi Guys, I feel as though the lights in my TT are not as bright as they should or possibly could be.
I've done a search on the site and can't find a definite answer, someone mentioned briefly but, didn't go into enough detail to satisfy my curiousity, so, can anyone tell me, do xenon light bulbs dim over time, plus do they run at 4300k or 6000k as standard, which is best?
As far as I know the bulbs in the car are the original ones, the car is nine years old now and them being gas discharge I wondered if they had lost some of their oomph and consequently that could be the reason they looked a little dimmer.
Anyone know or point me in the right direction regarding the best output to use 4300k or 6000k?
Tia, Jimbo

 

[NHN]

4300 is stock, they can over time lose there sparkle, modules are another, but bulbs are the 1st thing to check, higher the K the lower the light on the road, ideally 4.3 to 5k are best, 6k borders on visibility issues & even then they need to be good bulbs.