Entropy is a subtle and difficult concept that seems important in understanding consumption and the ability of a practice to continue over long timescales.
If after a long time intelligent life still existed on this earth, it must still be possible to withdraw negative entropy from somewhere. This conclusion is probably trivial and saying little more than that the sun must still shine, bringing the argument back to the one about useful energy and usefully concentrated materials. But there could be more subtle and important uses of the entropy perspective independent from energy e.g., with respect to distribution of materials, and information/culture/civilization as initiaded by Boulding. tbd
Entropy would seem to be linked to the existence of sentinent and consciously aware beings via the notion that these require the processing of information, which increases entropy. Thus increasing entropy in any other way reduces the amount of existence that can be experienced. The negative entropy sent by the sun to earth creates an opportunity for self aware existence, largely unused.
- Wikipedia's entry on entropy provides various aspects and a lot of links