I've replaced more brake lines than I would like to admit, here in the rust belt, they just rot away. I like to get short lengths between 1-3 feet and unions and piece together the lines. The short length make it easier to bend the lines and install on the vehicle with the body still on the frame. you will not need to double flare the lines since they are already flared and if you should ever have another failure, you will only have to replace a small portion of the line and not the entire piece.
I've also bought spools or line and custom built 1 piece lines from the master to the wheel cylinder. this was on a body off frame resto on my hotrod, nuless I am removing the body, I would not recomend this route.