You are kind of an outlier, but they certainly exist. In these cases it's extremely hard to do a kind of "comparison shop" between smoking and vaping, and yours is confounded by the fact that you've never smoked.
How much liquid do you go through in a day, that might give more of a sense of the type of vaping you are doing. If you are taking 1 second puffs and going through little liquid it might explain your ability to tolerate that high amount of nicotine in your setup. Or, you are just a nicotine outlier and for whatever reason your body just seems to enjoy and tolerate nicotine.
I can't really offer much on health effects other than nicotine does seem to possibly have (some mild, and oftentimes rather murky and random) some effect on your cardiovascular system. If you are concerned, I might go find a doc who has at least some working knowledge of vaping and run your particular amount of mg/day past him/her and see if you want to work on reducing it or not.
Also how did you get to the level you were at did you start there, or did you steadily increase over time, as brains will adjust to nicotine so if you are searching for a "buzz" or "Effect" by raising nicotine you will get to a point of diminishing returns, and in fact you may already be there. But if this is your "sweet spot" and has been for a while... well that is what it is.
Anna