I have a Z2, which has a "Lamp Replace" light below "Warning" & "Power." The Lamp Replace light came at approximately 3,000 hours (I suspect EXACTLY at 3,000 hours). I tend to ASSume plenty of safety factor built into specs, so I continued to push it for a while; however I did read somewhere that the bulbs can potentially burst, so I finally replaced the bulb at around 3200 hours. (Interestingly the Z2 gives no lamp life spec, but I don't think the projector "knows" when the bulb is ready to blow, and that the light was simply set to go off at 3000 hours).
The replacement was easy, but I was surprised the new bulb didn't increase my brightness as much as I had heard (some sources say the bulb's brightness reduces 50% over its life.) What's worse is that I now had a dreaded "dust blob" and some color irregularities. The left edge of my screen tends to be a bit reddish, and the right side, a bit yellow-greenish. Needless to say, I am a bit disappointed. I was careful during my bulb replacement, following instructions to the letter and cautious not to introduce dust into the projectors internals.
I love my projector, and hope this isn't typical of bulb replacements. I would love to hear other experiences; but the next time my light comes on, I will really be thinking hard about putting that $350 toward a new projector.