When a bulb is replaced in a projector (let's say a DLP projector, like the InFocus 4805 - just for example), is the projected image "like new" again or does the new bulb show the wear and tear of other parts?

Here's why I ask - I wouldn't mind paying a couple of hundred dollars 2 - 3 years down the road for a new bulb if it made the projected image look as good as it did from day one. If other parts, like the mirrors, are much longer lasting than the bulb then it seems this might be logical reasoning.

However, if other parts of the projector degrade but don't necessarily require replacing but their degradation causes a visible difference in the image then replacing the bulb for a less than new looking picture would make less sense.

Hopefully, my question makes sense.