They don't illuminate under the car , they shine upwards and are only visible when the door is open ( and the courtesy light is activated ) .....
No problems with mine , i guess it depends on how good a job you do wiring them in , and then looking after them ...
If you care for the car, there shouldn't be any problem with the illumination.
Problems happen when water gets into the ballasts (blocked drains etc) , but the EL technology is fairly robust otherwise .....
As posted elsewhere , you could get a set for an r170 for about a ton ....