As the title says, I've now got IR on my late 2012 27" iMac. When I first got it in mid january everything was fine. I did that check board grid IR test and I could leave it on for hours with no signs of IR whatsoever. What's strange is that yesterday I was working on my iMac for about 10 hours straight and not even the slightest signs of IR. Today however, it's actually the hottest day of the year so far where I live and now I get IR after just 10-15 minutes. Could the reason for it actually be that the overall warmth in my office has increased a lot, which then makes the screen get IR? I know it sounds weird but that's the only thing that differs from the past five months of using it on a daily basis and now BAM, there it is. It ****ing sucks.