That chart tells you more than i could type in 1000 words. there is really no reason to run cobs hotter than you can
i have run some citizen chips up over 420W each and they are barely bigger than a CXB. you really have to beat teh hell out of one of these to melt them. like greatly undersized heatsink+high currents
if you wanna blow up chips i recommend blowing up ones that arent so expensive