On the 757 there is about 30deg C increase in EGT when clb1 is selected at high altitude. Obviously there are flight phases like a go-around or take off that has much larger increases in EGT and yet it is quite widely taught in my company that it is big no-no to select clb1 in the last 2000ft of climb because of the possibility of 'thermal shock'.
I have never seen this written down and suspect it maybe an SOP left over from the dark ages.
Any comments?