The larger TBM would require ~7/4 more discs. So you might go a longer time between disc changes, but each disc change requires 7/4 more effort and material. An

The larger TBM would require ~7/4 more discs. So you might go a longer time between disc changes, but each disc change requires 7/4 more effort and material. Any hypothetical savings in spin-up and spin-down would be offset. If the balance came out to some advantage, it would not be due to a larger diameter of the TBM. It would just indicate that you should consider retrofitting the smaller diameter TBM with thicker discs.