An interesting limit?
Inside the Habitable zone is TOO close when the red giant phase comes?
Of course, the surface would be sterilised anyway, but there's something about a hunk of rock in orbit that maybe future life could re-colonise.
There would be issues due to the atmosphere and oceans being boiled away, as well.
Maybe life could only persist on large planets or moons of gas giants that were originally "outside" the habitable zone but still had an ecosystem based on a massively deep ocean and geothermal energy?