The Merriam-Webster Dictionary of English Usage (1989) has more than a page of commentary on this construction, including numerous examples of its use, mostly in reported speech. The speakers include John F. Kennedy.
Here are some passages from the entry on as far as (pp. 127, 128).
Our commentators, from Fowler 1926 to Harper 1985 and Einstein 1985
are nearly unanimous in condemning the construction; only Faris in
American Speech thinks it deserves more consideration. And why do they condemn it? As is so often the case, many do not give a reason.
Fowler did so perhaps because of novelty; but both he and others have
probably been affected by their frustrated expectation of the
formulaic verb goes or is concerned. Encountering as far as and
then having the verb withheld is a bit like not hearing the other shoe
drop. But as for novelty, it is not clear how much of a novelty the
construction is. [...]
There can be no question, after more than three quarters of a century,
that prepositional as far as is established in speech; it was
clearly established in 1962 when Faris published his findings.
Reference books have been slow to catch up in this instance. But
speech and reports of speech aside, the expression has made little
inroad into ordinary prose. Our most recent evidence shows it still
primarily a speech form.