I have a set of Demeyere Apollo stainless steel cookware that is 12+ years old. It has been used a lot and I have not exactly babied it. Sometimes I have badly burned them and have used steel wool a fair number of times. The surfaces are very scratched and discolored. They still function okay, it seems, but I am concerned about contamination from the surface being worn. I am worried the aluminum core underneath could be exposed. How would I know? Are there any dangers with continuing to use this cookware? Thanks!