I don't think Ni is necessarily just random "flashes of insight". Perhaps for an Ni dom.; but we're talking about NTP's for whom it is shadow. It's not going to come out so consciously and strong like that. It will instead, likely shadow our Ne (and thus be hard to distinguish from it).
I've been recently emphasizing this in terms of the different "special" function positions [in contrast to "general" functions anyone uses] are basically from the "complexes" (which are lesser senses of "I" alongside the ego). So for an NTP, it would be the Opposing Personality, or Witch/Senex, which are the parts of us that feel obstructed or negated, and then react in some usually negative way.
Ni itself [also been working on further simplifying function definitions] is a perception of "what could be", where a pattern is "filled" in by inferring meaning from an individual, impression (which is thus internal and also likely unconscious, like a "hunch"), as opposed to inferring from another pattern (in the environment), which is what Ne is. That's the difference between the two attitudes!
(And when I say "what could be", it's not necessarily "future" as it is often made out to be. I mean "could be" as opposed to "what is", which is the S focus, and a judgment function is really needed to add a timelike element such as what will happen in the future).
So yes, since it comes from the unconscious, it may show up like a "flash" of "insight", but this will be more noticeable for types who prefer it. For NTP's, it will be more like a background feeling that influences their perception. Like for me, a sense something is wrong in a situation (including something that was really desired, but then there's this fear that all is not what it seems. The Senex is said to be connected with an ego one-sidedness, so that when the dominant is too rigid [and the aux. filling in with its external iNtuition of comparing the situation to other patterns], such as in my sense of the way things "should" be, then when it looks like some things are working out that way, there will be this sense that it's "too good to be true", and likely, it will turn out to be not what it was cracked up to be, because the dominant was relied on a bit too much).
This does not usually come as a "flash", because of the fact that the function itself (not just the natural source of its impressions, but the "shadow" complex it is connected with also) is unconscious.