The copper supply pipes and Globe Valves under my kitchen sink are real cruddy looking green and white corrosion (?). The Globe vales are stiff and I've had to redo the stem packing. There is also a tee off the hot water line for the dishwasher. Other than the stems nothing else has leaked. How do you decide if/when to replace the pipes and valves? It is all original (28 years old) but that along with the plumbing work in the rest of the house is kind of sloppy looking, e.g. scorched joists around solder joints, etc.