Doris Lessing, Shikasta and follow-ups. That concentrates more on the fall of those civilisations, though; they only realise in retrospect that the "golden age" was better.
I was going to say Numenor, but tbh they were pretty short-sighted given their longevity. Like, cutting down all the forests in Numenor, then in Eriador. The irl British were were better at that, planting oaks for shipbuilding a couple of centuries down the line.
John Wyndham's "Trouble with Lichen" looks at the effect of an anti-ageing drug, and how that might change society, particularly women's roles.
Michael Scott Rohan's duergar in the Winter of the World series are portrayed as wise, technically advanced and able to withstand an Ice Age much better than modern humans. But you don't get much detail on that.
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I was going to say Numenor, but tbh they were pretty short-sighted given their longevity. Like, cutting down all the forests in Numenor, then in Eriador. The irl British were were better at that, planting oaks for shipbuilding a couple of centuries down the line.
John Wyndham's "Trouble with Lichen" looks at the effect of an anti-ageing drug, and how that might change society, particularly women's roles.
Michael Scott Rohan's duergar in the Winter of the World series are portrayed as wise, technically advanced and able to withstand an Ice Age much better than modern humans. But you don't get much detail on that.
None of those are quite what you want, sorry!