The reason you get pin holes in piping is called water turbulance. As the inside of the galvanized piping attracts calcium and minerals out of the water through ion exchange, it deposits it unevenly on the inside of the pipe. This creates a whirlpool action just beyond the growing debris. This whirlpool grinds away at the galvanized coating picking up minerals and calcium and using it like sandpaper. Once the galvanized coating is breached, the water corrodes the iron below and develops a leak. This can happen anywhere in a section of piping.
When you pull out your galvanized pipe, and look through it, you probably will not be able to see light at the other end of a 5 foot section. What you will see are small marble like mounds on the inside of the piping, blocking the water flow.
Copper is a good selection, because it resists the ion exchange. But you have to pretty much remove all old sections of galvanized, or you get a different kind of corrosion where ever the two types of material meet. This is called electrolisis, created by dissimular materials.
Probably a good time to have the whole kit and kaboodle changed out.