In the big Boeings I have flown, B747-400 and the B767, both with RB211s and GE CF6s installed, take off thrust EGT very rarely gets even close to the MCT limit because of de-rating.
Does that then mean I could operate at that thrust level contuously as long as the CON EGT is not exceeded? I don't, but could I?
No. The CON limit is a thrust limit as well as an EGT limit.