'far' vs 'a long way'

[Daemon99]

I read somewhere that far should be used in negative sentences and a long way in positive ones.

1) Downing street is not too far from here.
2) Oxford street is a long way from here.

Do native speakers really follow this distinction? I think I have seen people using far in positive sentences as well.

Eg: That's very far from here.
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Non-native speaker of English
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I intend to live forever - so far, so good.

[Mister Micawber]

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I, at least, have never knowingly made that distinction. 'Not a long way' does sound a little unusual to me, however. Nevertheless. 'should' sounds far too prescriptive for comfort.
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Native English teacher at Mister Micawber's