Car has soft and somewhat fading brake pedal. Pedal continues to slowly fall as pressure is applied. Car has all new genuine pads, rotors and both rear calipers. No fluid leaks nor air in system. My Saab mechanic has never replaced a master cylinder and discounts it being defective. A friend has a 2009 9-3 with similar pedal fade, but not as bad as mine. Any thoughts as to cause.

Problem appeared yesterday. Message says to make safe stop. Basically the car cannot be started.

I found a set used complete (Quick Strut) but they are off a Saab that had a 6 cylinder engine. What would be the ride height difference and would they create any premature ware on the rest of the front component's?

Mechanic quoted me $1365 to replace both front struts. Is this a good price? Is it safe to continue to drive for a few months? Is it even worth fixing as I paid $5850 for the car.