To emphasize a bit more what Gary said, coasting is either shifting into Neutral or the rather difficult trick of watching the left pie chart on the center console Energy Usage
display and keeping it blank - not even a sliver of power or regen. The only kinetic energy you lose that way is from friction - air against the car, wheels on the road, bearings and gears. Those losses always happen; they can't be avoided. So that is the most efficient way to slow down. That is what the hypermilers do. Frankly, I don't, and I don't get the mileage they get. Personally I consider a moving car in neutral to be dangerous, and keeping my eyes on the center console to be equally dangerous. The closest I come is moderating the accelerator so that only a single dot shows on the dash. That's only a rough approximation to coasting, but I can watch it with my peripheral vision while keeping my eyes on the traffic around me.
Now, as to what cwerdna said about GOM: You didn't use that term, and his reference may be puzzling you. But you did say, "We almost never charge to more than 80-85% and never let it drop to less than 30%." If you got your car in January I have to assume it is a 2012 model, not a 2013 model. The 2012 does not have any gauge that tells you percent of charge. So, like cwerdna, my guess is that you are referring to that big number on the dash that Nissan calls "Distance to Empty" and we call "GuessOMeter" or "GOM". It is only very vaguely related to charge, and it is truly a guess being made by a computer (I would say a badly programmed computer) as to where you are going to drive and how you are going to behave in the future. Please ignore it.
You do have a "gas gauge"; it's those 12 blue and white bars surrounding the GOM. When all 12 of those are gone, you are on "empty". Like a gas car, the gauge is calibrated so that "empty" gives you an early warning. But the LEAF gives you three much more specific warnings.
- The first is "low battery" which we call LBW. The GOM starts flashing when you get down to this point. It's nothing to worry about - you are really about as far from empty as charging to 80% is from full.
- The second is "very low battery" which we call VLBW. At this point the GOM "gives up" and just shows three dashes. You really are getting fairly close to empty at this point, and pushing much further might reduce the life of the battery.
- The third is "Turtle". A reduced power message pops up on the dash and a picture of a turtle shows up there. This, my friend, is just about the end of the road. Find the closest safe place to stop, and call for help. Hopefully you will never see the turtle, but even if you do, know that Nissan has programmed the car to protect the battery. It will stop the car, likely within half a mile, and there will still be a few percentage points of charge remaining.
So the next time the GOM says 30 just grin at your wife and tell her this little beauty hasn't begun to show you what it can do. You haven't lived until you hear the mellifluous voice of the lady who tells you how low your battery is.