I've had great experience with Viewsonic and Epson but since I have yet to see a Viewsonic device in Kenya, I would choose Epson. Bulbs do go out on these things.
In my experience, a high quality projector (HDMI/DVI connector, good electronics, etc...) doesn't need as much brightness because the sharpness makes it easy to read without needing the brightness as much. I wonder if you could get away with 3,000 lumens from a high quality projector. Maybe a store with multiple epsons will let you evaluate 3 different models for a day in your conference room?
Also, what's nice with epson is that it has instant off technology so it doesn't need a cool down period if the electricity goes off or somebody unplugs it. This really helps with longevity which is why I think Epson is the best brand for projectors.
-Adam