The maintenance manual for my 05 has "check brake fluid and pads" pretty much for ever scheduled maintenance. Other posts suggest that the pads and shoes should last way beyond 100,000 miles due to regen braking, but what about fluid?
It should last many, many years. You will probably get tired of the car and trade it in before the fluid will needs to be changed.
I like to do that every fall. I siphon the old brake fluid out of the reservoir, add fresh DOT 3, then start to flush/bleed all the brakes. You'd be surprised at the crap you get out. Even air! I took delivery of a new 2000 GMC Sierra and immediately noticed very poor braking. Dealer said it was "normal." I tried towing my 8,200 lb trailer and had to crank the trailer brake gain up so high the trailer was starting to lock the brakes. I changed the brake fluid and then bled/flushed the brakes. Got air to come out the rear disk brakes. My GMC brakes never did feel super strong, but they were way better than at delivery. It's "normal" my a**! I like nice firm reliable brakes. Over time, brake fluid degrades like any other fluid.
Keep in mind on an '04+, the brake flush is more complicated due to the brake by wire system implemented. You've got a fluid pump plus several valves, plus a manual bypass. I'd leave this procedure to a dealer or someone with lots of familiarity w/ this braking system if it ever needed to be done. However, when I used to do my own brakes on my non-ABS cars, I too would do a bleed every time I changed pads. Amazing how much firmer/more responsibe the pedal got once I got the air out.
Rick: That's what I'm worried about if I try to flush/bleed my Prius brakes. You can really bugger things up if you open a bleed screw and air gets sucked in. I'll have to ask the dealer if having somebody stomp on the brake pedal while I'm crawling around underneath works like it used to. On my 1992 Honda Prelude SR, the only way to flush the ABS motors was to use a special scan tool interface. On my 2000 GMC, the only time you need the scan tool is if you know you have air in the ABS module. As the ABS module was plumbed "inline" doing a normal brake fluid flush and bleed worked well. If there was air introduced into the ABS module, say during a major repair or master cylinder run dry, then the OTC scan tool was needed to cycle the ABS module pumps.
The repair manual warns that you may introduce air into the system if you don't use the handheld to bleed.
