Is there any advantage to running "break in" slides for a plasma? Some claim that it helps age the panel evenly, help porevent image retention which is more prone during the first 100 hours or so of use, or help the picture "settle" in for a calibration.

Any truth to this?

I just turn mine on and enjoy them, after tweaking the color, contrast, etc. to my liking.

I doubt there is any truth to it, nobody ever did this kind of breakin procedure for the CRTs we all watched. I did however run my S1 all night with the breakin slide I downloaded from AVS. I just watched what I wanted and when I went to bed I kept the TV on and let the slides run all night; it doesn't hurt it and if it does indeed help why not? Other than the wasted power and cost.

All this break-in talk makes me wonder, what couldn't benefit from some braking in?! Toothbrush, carpet, winter coat, oven, dishwasher, etc, etc

For the break in period I would just be careful of the material that you watch. If you are watching 16:9 TV without still images that are on the screen for long periods of time then it should be fine. For 2.35:1 movies and 4:3 content, just try to limit them as much as you can to be on the safe side. After that you don't have to be as careful.

I wasn't as careful when I first got my plasma and there is a subtle difference in black levels that shows up in the middle of the screen during really dark scenes. I played a racing game for 3 to 4 hours at a time during the break in period and I think that is what the subtle difference is blacks is from.

I hear that porn is the best plasma break in videos available. Your mileage may vary.

I don't think you (or anyone here) should ever make such a definitive statement about porn without asking me first.