If you don't go crazy with "enhanced, extra bright" halogen bulbs and stick with a good quality (Hella, Osram, Philips etc.) part they should last long enough to get dim with age - 5+ years. I've gone through two sets of "better" H11 bulbs in my Mazda3 and just ended up back with the original Philips (German) bulbs that came with the car. They probably have a total of 3 years use while the other ones I tried, which provided negligible improvement, lasted no more than a year. I found that more Lumens does not necessarily equate to better vision.