The connector wears with the chain. To me, a worn chain would equate to an equally worn connector.
I had difficulty finding the KMC re-usable links at the local shops. An ebay seller (usn.inc) had them to me in a couple days.
Some of KMC's links aren't replacable (per the mfr) for off the bike chain cleaning, if that's a concern for you. The re-usable Shimano links (MissingLink 10S) are labled as such on the package. They might also be stamped "CL556S" on the link itself.