So that means what, exactly?

Do heat cycles mean that the device only lasts half as long as it might if it were kept at some constant ideal temperature? A third as long?

If so, then...so what? The tinkerers using these things aren't broadly concerned about these things. We're all out here running our real-live desktop, laptop, and pocket computers with bursty loads, dynamic clocks, and dynamic heat anyway, and these things are generally doing just fine. We aren't driving space ships with this stuff; it'll be alright.

I insist that there is no merit to holding a lowly Raspberry Pi board to a higher standard than we hold everything else.

Furthermore: If perfection is necessary for some kind of application, then maybe starting with a <$100 hobby SBC isn't the best move. It might be time to look within for a better pathway.