Ok just for my own curiosity I did an EXTREME checkerboard test while I went to a meeting. 2 hours 10 minutes at full brightness and NO SIGN OF IR on my week 48 LG. I'm convinced that not all LG's have an IR issue.
I did the test as you said. No IR! So happy! (I was actually quite surprised. Also, If you read later in the disscussions pages you will see a person who did the IR test for over 2hours with bightnesss on full! And he said that it was a 48Week LG.