I happen to disagee with the other posters on this subject. Matter of fact, the painting of paneling and fireplaces is one of the most popular things to do now days.
I have painted my fireplace four years ago along with the paneling and the room is so much bigger and the lightening up is unbelievable. I have absolutely no, NO maintainance of my fireplace with it being painted.
It now looks more like the focal point of the room and shows off much better. And with a fire in the fire area, it is beautiful.
You will see in many mags. like Southern Living and Better Homes, fireplaces are transformed from the old brick to something much better.
Now, you are perfectly correct about once painted its painted for ever. This is no doubt correct. You can change colors add accent pieces and that thing, but you cannot ever come back to plain old brick.
Check out some pictures and others that are painted and make up your own mind.