> I’m skeptical that a 10-year-old MacBook is pulling 4-6 hours with the original battery.

It's more possible than one might think assuming usage of Safari with an adblocker installed and few or no electron apps running in the background. MacBook battery life for light usage has been great for a long time; where it fell short prior to the ARM transition was for heavier use cases.

They're great, but not magical. 10 year old macbooks never did 10 hours, even when new, much less with degraded battery.

I don't recall 5 hours from my 2013 tiny macbook air. It certainly doesn't last that long now - maybe an hour.

4-6 hours, not 10

Even that was a stretch I never got in any of them.

Yeah in general a macbook from 10 years ago would have a max autonomy of 9h if you get a dGPU. But in practice if you got 5h of use that was decent. Nowadays they last about 3H max in the best case...