Lamp life is an issue to consider if you use your projector several hours or more per day. Most DLP models give 1000 hours of lamp life; all LCD units offer at least 2000 hours, and in the case of the Proxima Ultralight LX1, 4000 hours.
Lamp replacement cost generally runs around $400 for this class of product. If you plan to operate the projector two hours per business day, this equates to 500 hours of usage per year. At this burn rate or higher, lamp replacement costs should be factored into your total anticipated cost of ownership.