With apologies for inserting pragmatic queries into a mostly theoretical discussion, going back to your #8 comment, Neil, do you recall from your testing approximately what length of hold at cone 4 achieved cone 6 (and also the hold at cone 6 to achieve cone 8?).
And what effect might firing to a lower temperature and holding to achieve the heat work associated with a higher cone have on an electric kiln? My theory is that, if done consistently, it may prolong element life but wear out relays faster (assuming they are not solid state).
I have recently moved to ceramics from working with fused glass where heat work is a well developed and quantifiable concept as there is less variability in the chemistry of the materials. Firing as "low and slow" as possible is often preferred to maximize control and consistency of the end result. I'm curious about the transferability of this to ceramics.