Legairre..... have you heard "stories" about the "compatible" bulbs being offered for theMitsubishi Projector Lamp - VLT-HC910LP ?
As to the question about when is a "reasonable" time to change the bulb... boy that's another one you will get multiple opinions on. I know folks that change their bulbs at 500 hours... and others that go 5000.
Your individual bulbs life is going to be determined by 1. manufacturing quality 2. your operation of the projector 3. Luck.
Some bulbs just fail early... some batches are poorly manufactured... the only thing you can control is how you operate the projector.
Do you turn the projector on and off like a TV?
Heat Shock is what kills a "good" bulb.
Once the projector is turned on... let it run until the temperature in the projector has stabilized... how long is that... probably 30 to 60 minutes.
Once the projector is off... leave it off until the bulb and projector have returned to room temperature... how long is that... good question... but probably at least 2 hours.
Some bulbs burst at their "end of life" others just go black... none of us have any clue as to how each individual bulb is going to react. But the heat stress on the bulbs' glass and container surely has a deleterious effect over time.
Personally I just got the message from my HD1000 that the bulb would need to be replaced soon... I reset the clock and am proceeding on for now.
The bulb in my InFocus 7210 has ~3,800 hours on it and is still bright even in low power on my 135" screen. I still have a brand new bulb in the box for the InFocus.... so I may go ahead and change it out in the next couple of hundred hours... I do not need to set any records, but I do like to get my moneys worth... if possible.