Only one of my B67 saddles (with springs) squeaked.
It turns out it was the ball-n-socket joint at the very nose of the saddle. Bill at Wallingford talked me through greasing various parts of the saddle frame, and greasing the ball and socket solved it. No more squeak at all.
My 2nd B67 (honey leather for the gold bike) I greased right away. Not a peep!
The springs definitely add to the risk of squeaks and creaks. Once I figured out what part of the frame my cycling style made squeak and greased that, all was good. I really do like the springs. They are worth it to me!
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson