Chris, you mention your car has 280,000 km and the caliper pistons were rust-free with no pitting.
Were the caliper bores also in good condition?.... are the calipers original?.... what brake fluid flush schedule did you follow?.... and where in Canada do you live - Maritime Provinces?
What I'm getting at is to see if your case can be used as poster-child for rigorously following brake flush recommendations of flushing every two years, and that it really does pay off to go through the trouble. What's your story?
95 E320 Cabriolet, 131K