I just replaced my brake fluid on our 2014 Leaf with 66k miles. I did not see any record of this work having been done by previous owners. The old stuff was pretty dark, which did not surprise me. I used a brake fluid tester to see how bad things were. The old fluid in the reservoir had 3% moisture, the fluid first coming out of the caliper nipples had between 3-4%. Well, I say at least 4% as that is the highest level that can be measured and it could have been higher. When replacing, I measured the moisture of the fluid coming out of the nipples periodically until it measured 0% (new). I needed 2.5 bottles of the Nissan DOT3 fluid to complete the job, using about 500 ml to replenish the reservoir after draining and getting fresh fluid out of the right rear, which is the first according to the service manual for '14. I used about 100ml for each of the fronts and about 150 ml for left rear.
A couple of takeaways. One is just how much difficulty I had with emptying the reservoir. I could get out the top 1/3 but the old stuff stayed in there. If there is a trick I could not figure out, please share. The other thing is that I tried to pressure bleed the car but struck out. With other cars, I would have the car with ignition off, put the cap on the reservoir, pressure it to 15 psi, open a caliper nipple and away I'd go. With the Leaf, I noticed I got just a bit of fluid and a lot of air out of the first nipple but the reservoir level did not drop much. So I switched to the using the brake pedal to move the fluid. Again, if I am missing something, I would love to know.