Im in the same boat as you with my ED30 also mate.
Im sure the lights lose their "crispness" over time but i dont think it is too noticeable. I think the glass on the lights become cloudy and scratched over time and that can affect light output.
Either way, if you are in the market for buying new xenon bulbs, please be extra careful as there are plenty of fakes out there - especially on ebay!
Hope this helps,
Rich