When I bought my K11LT I had a sticky front caliper. Bike came with all maintenance records and I went through it. No mention of brake fluid change.
I did the bleed and what came out was atrocious. Caliper still sticky. Against strong advice from across the pond I bought a caliper rebuild kit and did the work. I was told by this person across the pond that invariably, if you split the caliper, it would leak. Not so.....
Anyway, I figured that the master cylinders were going next and I had the source handy for the kits so I pulled the trigger on the front and rear. They still sit in a parts drawer, untouched....maybe someday.