Here's a pin from the most worn chain I've ever seen. It was worn a whopping 3/8" over 12" of chain. I consider a 1/16th wear time for a new chain.
This chain was so bad that (of course) the chainrings as well as the cassette were toast. The chainrings were so bad (just stubby teeth left) that the guy had gone OTB (over the bars) when he stood up to pedal and the chain skipped on the big ring.