The lamps are meant to be replaced every 12 months. I'm not sure why, probably a marketing scam! There is a counter on the power box, and it shuts down after 365 days and just keeps bleeping. I've figured out how to reset the unit though, so I'll keep doing that until the bulb actually blows
Not sure if efficiency is affected or not, but at $350 a go I'll take my chances!
Anyway, it costs peanuts to run power wise.