Author seems to have built 5 systems from 2016 to 2023, or around every other year.

Some parts (e.g., RAM) are re-used across multiple builds

It's interesting to wonder: How much $$ is the hardware cost vs the lifetime energy costs? Is a more power-hungry machine that would operate for 4 years better than one that would operate for 2 years?

The motherboard + CPU is USD 322 right now on pcpartpicker. At USD 0.25/kWh (well above my local rate but below the highest rates in the US), 36W continuous over 4 years is also about $315. So, a ~43W, 4-year system might well be cheaper to buy and operate than a 7W, 2-year system.