I was at the same seminar as Sean and Sanjay. Sanjay, whom I and 100K others, think is the utmost authority, States that even at 18 months the bulbs loose less than 10% of the par. He states, based on his reaserch that the bulbs just require more electricty to obtain the par, in a basic conclusion...they are still efficient at 18 months but requrie more electricy to function. Just my $ 0.25...

Steve