LED lamp life expectancy depends on fixture type and usage scenario. LED application to automobile is too new to have any creditable data for reliability concerns one way or the other. For household LED lighting according to the claims from various manufacturers, the life expectancy is 20,000 to 50,000 hours. At 8 hours per day this would be approximately 7~17 years. Supposedly Mazda uses the best quality LED's, this is roughly 30 times longer than incandescent bulbs and 5 times longer than compact fluorescents. So if you replaced your halogen headlight bulbs once for the period of owning the car for 10 years, you may never have a chance to replace your LED headlight unit unless you own it for 300 years! Of course sometimes the environment such as high temperature will cause supporting electronic circuitry, i.e. parts such as capacitors, fails, or even the LED itself fails. But it should be very rare. I'd just enjoy the benefits of the LED lighting and not too worried about its longevity.
Good sound comment. But I would like to add some info here as I design LED product for industrial lighting and now recently, the driver circuitry for train/rail headlights.
Remember, LED lifespan is based on not when they fail, but when they reach typically 50% of there brightness. As an LED ages, its output diminishes. Its not constant. So way before the expected lifespan approaches, you may find them getting a touch too dim.
The big factor that dictates lifespan is temperature. If LEDs run too hot, lifespan is reduced. The design needs to ensure that the LEDs are properly heatsinked to maximize lifespan. Problem here is that a designer is always trying to maximize lumen output which results in hot LEDs. Some of the LED product shown in the modification threads looked horrible. Cant see how they going to last.
LEDs have come a long way. LED failure used to be pretty common in products. A lot of LED product has probably got a bad reputation because of this. However, LEDs have improved a lot over last couple of years. In my experience, the issues that kill LEDs of late is still plentiful. I look at a lot of failures to determine the cause. The most common failure is the LED driver which in turn can destroy the LEDs. Voltage surges is a big issue. Strangle enough, component failure in the LED driver is not something I see very often. Electrolytic capacitors used to be an issue, but not so much anymore.
The next major cause is water. Water and moisture can be a menacing problem in that moisture can creep down a wire between the copper stands and the outer plastic insulation. I have seen moisture travel through 100 meters plus of cable to LEDs and then destroy the LED PCB board. LEDs are small and the anode cathode connections can be very close together unlike a bulb with a much bigger gap between contacts. The reduced connection gap of LEDs means a much shorter distance corrosion must travel on a PCB to become a problem. I have seen LED product catch fire because of water and corrosion!!!
Then there is vibration which leads to a bad connection that makes and breaks. This eventually leads to failure. But this applies to any electrical item.
Now the companies I do work for are always trying to up the warranty period or guaranteed life cycle of the product. You know what ... 9 times out of 10, it bites then in the butt. With LEDs, something always goes wrong. A warranty of 2 years is reasonable. Beyond that, you must specify what kind of fault you will cover.
Just out of interest, a common problem is that the end user expects the product to last a long time with no maintenance. ... so they install it in places that required a crane or cherry picker to access which results in huge costs just to change a LED bulb.
If Mazda need to replace an entire fitting as the LED bulb cannot be accessed, it a huge mistake. There is no need to do that. Sound like a money making racket. For me. I am happy with my HIDs. They are fantastic.
Brian