What additional wear or inefficiencies are there from inverting a AC signal to DC from say, 59.99 hertz instead of 60.00 hertz? And is there additional wear on transformers? How do small deviations from 60 hertz negatively affect equipment?
There is no significant effect on other than old-fashioned synchronous-motor clocks and timers, it’s more important that all the power sources are at the same frequency and very similar phase. If the frequency were to wobble rapidly there might be other effects but that’s unlikely with conventional fossil fuel, hydroelectric or nuclear power.