[andrewstuart2]

At least in firefox, I'm not sure that's true. I go back pretty frequently (maybe you mean specifically with vimium back navigation) and get yesterday's cached HN front page, for example.

[qolop]

The bfcache doesn't just store cached resources like static files but the entire javascript heap. It makes back button action instantaneous.

I've observed the effects on both Firefox and Chrome and it's like day and night.

On chrome you can even test it using Devtools > Application> backward forward cache