What Is the Relationship between the ‘Power Efficiency’ of an ASIC and Its Longevity?

An ASIC's power efficiency (low J/TH) is the single greatest determinant of its economic longevity. The more efficient the miner, the lower its operational cost, and the longer it can remain profitable as network difficulty increases and the coin price fluctuates.

A highly efficient ASIC will remain economically viable for a much longer period than an older, less efficient model.