I'll have to admit that I got a little lost in all the preceeding posts so I may not fully understand the original question.
given that there is a major annomaly in the operation of the aircraft e.g. an engine out the type certificate I read seems to put the time limit on the temperature limitation at 10 mins.
It defines the limitation based on EGT readings although the thermal damage if any is likely to be in the HPT.
Under most conditions all the thrust and aircraft performance that you need should not even approach the temp limitation. But for those conditions where it does approach or exceed the temp limitation your sense of the onset of serious damage will be a step change increase of EGT above the limit
just food for thought