Wouldn't moisture laden, worn fluid contaminate fluid as it comes out of the bleeder screw? The reason I ask is, when I bled my brakes, which I do not believe were ever done (bike is an '06, bought it in '11), , the stuff came out jet black, and in the process, ended up coming out perfectly clear just as it came out of the bottle! I would think that the fluid would be contaminated with whats in the caliper, even though it comes out of one side of the puck.
I would also think that as the fluid comes out one side of the puck, because there is no air in the system, it would 'suck' the fluid out of the brake caliper. The same type of setup is used for those little garden fertilizers you stick on the end of your hose, liquid fertilizer is in the bottom, a hole is on the top of the bottle, and water runs on top of it. The water running on top sucks the liquid fertilizer out of the bottle.
That takes a while, but take a thicker fluid, no air, and much less of it, and I think the same COULD happen with a brake caliper. I'm not an engineer or a mechanic, but it 'makes sense' that this is the reason why fluid might be replaced in the caliper!
I'll test your theory though if I remember at the beginning of next season when I bleed my brakes again! I'll pull the calipers apart and see if the fluid on the inside, after the bleed, is clean and clear, or has evidence of being beaten up with heat, moisture, etc.
I did experience markedly improved braking power after bleeding a bike that had not been bled in 5 years though.
"8 But God demonstrates his own love for us in this: While we were still sinners, Christ died for us."
Romans 5:8 (NIV)
2014 Kawasaki Vulcan 1700 Vaquero ABS SE
iPod Connector Kit, Kuryakyn Highway Pegs, Mustang Touring Seat, Marvella's Hitch, Kuryakyn Trailer Wiring Kit, Haul-Master Tag-a-Long Cargo Trailer
2011 Honda Shadow Aero 750 (Wife's)
Memphis shades quick-release windshield, OEM Solo Seat, Mustang Fender Bib, Chrome Solo Luggage Rack
Past: 2006 Vulcan 900 Classic LT