In racing fractions of a second make the difference between winning and loosing. ABS braking is slightly slower than non-ABS braking. A good rider/driver needs that extra control in braking.
In other words you might say ABS is for bad riders.
Hd suggests every 24mths a full flush. Last one was about $70? from HD using their factory tool. Car manufacturers recommend the same.
All my road bikes now have ABS, the last bike I sold VFR 800 didn't have ABS but had linked brakes. I would have given up ABS on the Harley if it had brakes like that bike. I guess I try not to ride on the road like I need to rely on ABS, and it you are stopping at the rate ABS is coming on it your stopping really fast, that would get pretty tiring for me on a 4 hour ride. I have only had ABS come on once and I was doing about 40km/h and a car pulled straight out on my left without looking my direction. Id prefer to have a bike with it and ride not to rely on it.