Moi has a 52 inch Toshiba DLP. The unit probably averages less than five
hours per day. The bulb lasted about twenty months although one of the
selling points was that it would last three years with longer viewing hours
Toshiba and the salespeople lied, imagine that!
Fortunately the extended warranty has essentially paid for itself with the
first bulb replacement and at this rate I will make a "profit" if this
replacement bulb lasts the same or less as the original.
However one of the advantages of a DLP such as the Toshiba is that barring
catastrophe, like failure of the DLP or light wheel, the unit should give an
as new picture for many years as long as you change the bulb. It is unlikely
current plasma/lcd (non-projector) can make than claim.