2007 Outback Brake Issues?

I am still driving a 2007 Outback with 238,000 miles on it. This week, the brake pedal went very soft, so I nursed it to my mechanic.

The mechanic says it’s the brake lines. They have deteriorated from years of Wisconsin winters, and need replacing. As Subaru places the brake lines inside the frame rails, this will be a costly job.

Have any of you been through this repair? Is it even worth it, or should I just donate the car as a tax writeoff?