As yet and Long ago

As yet adverb - Used in negative statement to describe a situation that has existed up to this point or up to the present time.

Long ago and as yet are semantically related. In some cases you can use "Long ago" instead an adverb phrase "As yet".

Long ago adverb - Of the distant or comparatively distant past.

As yet and long ago are semantically related. Sometimes you can use "As yet" instead an adverb phrase "Long ago".