LCDs don't have screen burn in the same way CRTs do. For CRTs, the burn is permanent. Once the phosphors are gone, they're gone. For LCDs, though, it's temporary. You can fix it by using the complementary image for a while, or just leaving it off for a while.
I used the same LCD for about three years, then gave it to a friend, who's still using it.
Formerly of Amptron