The old CRTs had three permanent tubes in them. They had to be dismantled to replace them but they lasted like 30,000 hours. You can still get them used here and there.
Current LCD, DLP and LCOS projector bulbs last anywhere from 1500 to 3000 hours. That means the lamp will last anywhere from a year to 5 years depending on how much you use it. It would be a shame to have to throw it away when the bulb burned out, so you can replace them for $200-$400 rather than spending $1500-$3000 on a new projector.
Laser or LED projectors will be a few years away. When they are on the market you could expect very very long lamp life (30,000 hrs +). That technology is only in its infancy right now though.
no, just get a used projector on ebay that has a lot of hours on it, that way when it burns out, you wont have to pay allot of money for a new bulb, you could just buy a newer protecter if you like.