A side note on a side note, they aren't immune to being damaged either...1. What problem are you trying to fix?
2. Upgrading to rear discs does very little to improve braking since the fronts do nearly all of the braking.
3. SS lines will do very little the improve braking. OEM rubber lines don't flex as much as the ads in the magazines will lead you to believe.
4. motul brake fluid is good stuff, but absorbs moisture quickly. Fluid like ATE superblue and ATE type 200 gold are a better choice for a street car... Unless you want to bleed your brakes every couple of months.
On a side note, I did some research on SS lines a while back. They were not created to improve braking or brake pedal feel, etc... They were created to keep people from getting their brake lines cut by debris on the track.