I checked with our local Hampstead rep, and while the LED is expected to last the the lifetime of the fixture (much in the way you would expect the LED in an alarm clock to last its life) he mentioned that most of these fixtures carry a one year warranty. I would investigate this, as a fixture that lasts it's first year free of gross defects is likely to last its expected life. Your client will probably want to change the fixtures long before the LED will need to be replaced!