One delay after another- in changing my calipers, I noticed the brake line nut to be very rusted. I took the necessary steps (1 day lube, a little heat and perfectly sized quality wrench) to avoid ruining this nut. Anyway, I ended up rounding the nut with very little effort. Same issue at the other end of the line too - after a few hours, I gave up and had to cut the line. I'm in the process of drilling out the nut, should I just replace all the brake lines in the rear(specifically, the intermediate line that connects the two rear lines)? I have very little space to do so and everything is rusted badly - I'm also afraid I'll ruin the receiving end in the process, possibly causing a leak I can't see.

I hope someone has some experience in this area since I've never had a brake line nut round so easily - I don't get it?