Self-sufficiency would mean no decent wine, no dark chocolate and using mutton fat instead of olive oil ......no thanks. In any case humans haven't been self-sufficient since they lived off grid in caves with no council tax but plenty of fish, game, fruit and nuts. There was time for idling, sunbathing, swimming and board games using stones.
I doubt if our crofting lifestyles are any more sustainable those of urban dwellers. Just about everything has to be imported with consequent food miles, fuel miles and additional costs for everything. It'll be even more expensive once the Royal Mail is privatised if we get any deliveries at all. We'll have to drive to Ft. William to collect our letters and parcels from a mailbox.