According to Boeing:
From a fuel consumption perspective, a full-thrust takeoff and a full-thrust climb profile offer the most fuel economy for an unrestricted climb. However, from an airline’s cost perspective, this must be balanced with engine degradation and time between overhauls, as well as guidance from the engine manufacturer. The airline’s engineering department must perform the analysis and provide direction to flight crews to minimize overall cost of operation when using takeoff derates or assumed temperature takeoffs and climbs
On repeated full-thrust takeoffs and climbs, the parts that suffer the most would be the combustor, hot section seals and HPT airfoils. Below is an interesting presentation given by Rolls Royce on this subject:
Derated Climb Performance