good scenario but wrong theory.
W = mad; you will be creating the stresses on an rb30 at lower rpm due to the higher forces generated by the extra weight and stroke length of the rotating assembly per revolution. They will wear out the same as a 26 revving much higher.
rb26 has less rotating mass, less acceleration due to the stroke length being shorter, and travels less distance.
As for your theory of stop start stresses the only difference is weight, the more weight the more forces on the rotating assembly because of the inertia resisting the change in direction, and again the same stresses happens at a much lower rpm in a 30 than a 26.
Thats why a built and full balanced rb26 on or off boost spins up at a faster rate and can safely rev higher/ much higher
And dont think an rb30 on song is going to be a tame beast, both will require throttle control coming out of slow corners.
A 30 is easier to drive but its no better or worse than a 26..... With all things being equal you wont kill a built 26 changing gears at 8k but you will kill a 30, and a 30 will be a torque monster at 4500 where a 26 will just be coming on song(with -5s that is), , because they are different and need to be driven differently.
and did I mention 26s sound better????