Correct, digital projectors don't suffer from burn in. The lamp in a digital projector operates at a fixed brightness. That light is either blocked or reflected away from the lens to achieve varying levels of projected brightness. These parts that block or reflect aren't subject to uneven wear. The lamp's performance will change over time but it's consistent across the image.

A CRT projector uses an electron beam to excite phosphors so they glow. These phosphors wear over time and become less bright. So ones that have been used more are dimmer.

-Dylan