The lifetime estimation approach, which has been developed, demonstrates a satisfactory estimated number of cycles until crack initiation on unnotched specimens, while the adaption for T/H design is still ongoing. Moreover, based on critical plane approaches and energy criteria, the handling of multi-axial stress and strain states on the T/H, for instance to calculate one-dimensional equivalent stress and strain paths required as input variables of the lifetime approach, are investigated. Alternative fatigue damage methods, e.g. based on micro crack growth, are also focused. In addition, the analysis of microstructural phenomena should help to enhance the creep fatigue interaction together with a more detailed failure description. It is assumed that tensile and compressive stress has equal effect on creep, and no distinction is made when calculating the creep damage. Current testing results illustrate that for GJV this assumption is astonishingly justified, at least at two sample temperatures. But there is a demand for a refinement to describe creep characteristics, also for aged material conditions.