Yep, both my BMW and Acura recommend a change every three years for this exact reason.
Gonewild wrote:These chemicals are hygroscopic, that is they have a tendency to absorb moisture.
This has nothing to do with the Leaf being an EV and has everything to do with keeping the system operating for the long haul.
Brake fluids are a type of hydraulic fluid. They must transfer the force from the pedal to the wheels. They must also protect the metal and rubber parts, lubricate, remove heat from the wheel cylinders, release air bubbles without foaming, handle some water - and keep it from reducing performance or damaging parts. The additives are depleted as they are used, and the brake fluid can only hold so much water before it's saturated.
The brake system is not sealed. Any system that heats some during the day and cools at night (brake system, fuel tank, crankcase, oil drum, etc.) will 'breath'. Daytime heating causes air to expand and the container 'exhales'. Night time cooling causes the air inside the container to contract and the container 'inhales'. The inhalation brings in moisture (humidity is higher at night) and can bring in other contaminants. It doesn't matter if it's an EV or ICE, and doesn't matter if the car's driven or sitting in a barn.
That's how the water gets in...then what?
Most brake fluids are alcohol based (the DOT 5 fluids are silicone based but not generally used in passenger cars). Alcohol 'binds' water - the water is absorbed into the brake fluid solution. Eventually, the fluid can't hold any more water and it stays in the system as a liquid. Fluid with water has a lower boiling point - and water's boiling point is lower still. Boiling makes steam, steam compresses - it cannot transfer power. Water is more dense than alcohol - and the water settles to the lowest parts of the brake system - the wheel cylinders where it causes rust and deposits to form. Water is not a good lubricant. The wheel cylinders use a rubber 'piston ring' to keep fluid inside and the rubber is damaged when it's dragged past the rusted/pitted wheel cylinder.
The rubber seals in the master cylinder and brake cylinders wear and leave particles in the fluid. There can be metal wear particles and dirt as well - air is dirty and the brake system doesn't have an air filter. Toss in crud, water, and heat and then rust particles and the brake cylinders become a muddy mess.
Per the Nissan service manual, there's nothing special about bleeding the brakes on the Leaf - any shop or even owner can do it. http://en.wikipedia.org/wiki/Hydraulic_fluidhttp://www.mightyautoparts.com/pdf/articles/tt136.pdfhttp://www.ehow.com/facts_7429801_brake-fluid-problems.html
It's a LOT less expensive to change $4 worth of brake fluid every couple of years than to change a single wheel cylinder.