Reconditioning Brake Lines

Impossible to tell the internal condition of the lines.
Use common sense. How old are they ? How often was the fluid changed ?( probably don't know that one). Do you trust your life to lines that are (insert number of years) old ?
How much are new lines? Are the rest of the hydraulics new or just cleaned on the outside ?
That is like a rattle can engine rebuild.
Clean and detailed the outside while still using the old internals. It looks good but ...