The preposition and adverb insofar, meaning to such an extent, is one word in American and Canadian English. It’s usually three words, in so far, in varieties of English from outside North America—though the one-word version is gaining ground everywere.
In many cases, the formal-sounding insofar as could be either removed or replaced with a shorter alternative. Even the three-word as far as is shorter (in syllables) and usually more natural-sounding than insofar as.
For example, insofar as could be shortened in each of these sentences:
In so far as [As far as?] it goes, this is a great little idea. [Telegraph]
Of course, even 3-D has its limits, insofar as [remove insofar?] films, photographs and paintings will always necessarily function as inadequate representations of reality. [Wall Street Journal]
The first option tends to follow the classic addiction model, insofar as [in that?] the foods that are known to trigger the most intense cravings are eliminated indefinitely. [National Post]
Now, insofar as [as far as?] media advertising is concerned, the message is not made by politicians. [Winnipeg Free Press]
But insofar as works well and is not easily replaced when it means to the extent that—for example:
The depiction of sex in the show is arguably one of its distinctive aspects, and cheesy only insofar as sex is fundamentally absurd. [The Atlantic]
I am obliged, in so far as I am able, to write about the world as I find it to be. [The Age]