^^ I completely agree..... the rate of progression of water into the braking system is not likely to be directly related to the presence of moisture on the rubber....
If a portion of the braking system is submerged for a length of time, there is an increasing probability of water getting into the system. If the pistons move against the seals in the calipers, there is a stronger chance of intrusion.... water is trapped in that area any time the bike gets wet. Capillary action would keep the nooks and crannies wet for quite some time. I would think that heating up the brakes to evaporate out any trapped water would be a good idea.
As the pistons normally only move a .010" or so, the seals don't actually 'slide' on the pistons -- they just rock back and forth. Maybe, they stretch a little and maybe that creates a slightly higher chance of water ingress....
On a side note, I have made it a religion to toss out any brake fluid I do not use, when I open a new can to flush braking systems. That's why I always buy the smallest container I can find....whatever I do not use is thrown away. Even if it's cheaper by the gallon, the total cost is effectively whatever I pay for the whole container.
Gawd are we in synch, or what?
I believe the introduction of water molecules into the system is via a transport mechanism of the dirt/brake pad dust, etc.The O2 in water is such a unfaithful whore that quickly leaves its H2 mate(s) in water and adheres to a myriad of other molecules in the debris. Only to recombine with with Fe (iron) components in the caliper/rotor transforming via redox (gain of electrons & a loss of oxidation, vs oxidation which is loss of electrons & a gain of oxidation); this results in Fe2O3, iron (III) oxide, a.k.a. rust.
There obviously would be other 'Rust' type reactions with other elements, again, because that harlot O2quickly 'loses interest' with whichever other elements it has temporary shacked-up with. Only to flit on to another.
This leads to the point I made previously regarding getting all the braking done prior to entering the water. Keep the sphincter-like pucks in place to dissuade the introduction of the unholy mixture of douche-water to the brake system.
And yes, I too would perform a few quick/hard stops to build sufficient heat to encourage the evaporation/boiling-off of any water that just might have wend its way passed the pucks. Periodic Maintenance
: Another fabulous reason why it's very important to disassemble the caliper, pulling pads & the pucks, sanding any offending areas, remove dust from work performed (see above: why this is important), and re-install pucks using a high-temp grease, etc.
And once again, I concur completely regarding purchasing smallest brake fluid container. I might save the remainder for up to 4-wks, because somewhere in that period, I'll perform the same process on my wife's R6. Then I discard any remainder. I make a point of not even purchasing the DOT 4/5.1 until shortly prior to addressing the brake system.