I was reading the manual for our Infocus 7205 the other day and it mentioned that once it reaches a pre determined hour mark it will display replace bulb each time at startup. I imagine its via a predetermined hour mark unless its measuring current usage or something...

Anyway that led me to believe you could just reset the lamp timer and get more use out of it until it really did burn out. I'm not sure what risks there are in this but those bulbs are not cheap!

Haoleb's Audio/DIY Website