one word or three?
Merriam-Webster.com lists it as one:
Main Entry: in·so·far
Function: adverb
Date: 1596
: to such extent or degree
But...what about the 'as'? In so far as I've generally
heard, this is the norm. Unless, for ex., you say, "You can go in so far, and then have to turn around and come back".