I feel like it's just there all the time. I don't notice using it, I suppose. However, it could be said that it shoves at me and I'll notice a feeling or a motivation that hasn't been expressed by someone. I can usually tell when people are being truthful... or not. I tend to rely it on it, almost implicitly... however, I do recognize that there is always room for error.
"It is not length of life, but depth of life." ~ Ralph Waldo Emerson
It's always there and running. My brain is ceaselessly buzzing with ideas, traveling down a concept map of the world around me, connecting seemingly unrelated ideas together with something I feel subjectively relates to them, a symbolic interpretation of the world. You could place a lightbulb in front of me, and I would focus on how each of the parts work together to make it light up, but also focus on what it means to me. It's weird, since I was a child, I possess a symbolic/aesthetic view of the world around me, and sometimes I could envision other things within an object. For instance, when I was little, I could look at wood grains and not just see wood grains, I would see faces or scenes within them.
With people, I tend to pick up a general vibe about them... can tell what characteristics they have without even asking, even if their intentions are good or bad. One person I had met gave me a particularly negative vibe that I couldn't put my finger on why, but I just knew that they were bad news.
Theoretical knowledge is more of my Ni-Ti loop... I can understand how systems work, and how they are related to each other, what types of effects one leverage point has on the whole system. When making an important decision, I withdraw from the world and focus on a solution that will end up creating the desired end result... focusing on which levers in the system that will create the vision for the future I see.
Trouble is, Ni tends not to see the restrictions of reality, which can be a problem in my case!
“Thoughts are the shadows of our feelings -- always darker, emptier and simpler.”
― Friedrich Nietzsche
My Ni is always there and working furiously. I don't notice that I'm using it in any particular situations - it's just always there. I'd probably noticed if , for some reason, it got switched off or something. My Ni is always present and alert, it helps me put together clues and vibes I get from other people and read them right - and so behave accordingly. I consider my Ni to be a useful and fine-tuned tool for survival
We could learn a lot from crayons. Some are sharp, some are pretty and some are dull; some have weird names and all are different colours, but they all have to live in the same box.