In the price range, most projectors have two year warranties. There are even a few one year warranties. About the best are Optoma's HD8300, and Epson's Pro Cinema 6010 which have three year warranties. The Epson even provides a 48 hour replacement service for all three years, while Optoma's replacement service only covers the first year. This Mitsubishi HC7800D projector's warranty is close behind.
Here are the warranties from some other popular projectors: Epson's better known Home Cinema 5010 has two years (with replacement), BenQ offers up only a one year warranty on their W7000. Additional projectors with shorter warranties include the JVC DLA-RS45, Sony VPL-HW30ES and the Optoma HD8300. The Panasonic PT-AE7000 has a one year warranty, plus a second year when you register (but with a 2000 hour maximum - which isn't that long).
The bottom line: Three years is about as good as it gets. Sure a replacement program would be nice, but the Mitsubishi HC7800D warranty is as long as any major brands, and longer than most.