Jonty: I appreciate where you are coming from. In the late '70s when I was flying the 707 my then company paid to use a procedure which had been devised by PanAm which allowed the use of MORE than Max Take Off Thrust out of Nairobi. So, the expected EPR was increased and the only "hard" limitation applied was to the max N1 rpm. This allowed an increase in both the field limit weight and also the second segment climb. We understood that effectively engine life was being "sold" at any rate I never had any engines give out using this procedure.
With more modern engines I suppose that the only time real TOGA is used is for the initial stage of a go-around and certainly seldom used for take-off.