re:  Change it at least every two years because it attracts moisture
(what does this do?)

When they are used, brakes get hot.  Water boils at a lower
temperature than brake fluid.  If water in brake fluid boils, it is
just like having air in the system--boiled water is a gaseous matter
state, just like air.  Unlike liquids, gasses are compressible.  Push
pedal, air compresses, no brakes.  This is known as brake fade.  It's
bad.  Especially coming down a mountain or the like.  Rust is the
least of your worries.

PS:  In a recent NASCAR auto race, front brake discs were seen glowing
red.  "The Professor" reports brake engineers advise this requires
1300 degrees F to occur.  Water boils at 212.