I did some Googling and web surfing, looking for some added information on any issues with the Specialized Epic line, and perhaps to find out when they insulated the tubes from the lugs. I found some posts by Bryant Bainbridge of Specialized. From 1980 - 1990 he was director of R&D there. He commented that as he wasn't there at the time he doesn't know when the insulating started, or if it was done on the '93 models. He also stated that separation issues didn't extend through the years but was only an occurrence on the first shipment of bikes. That would be what... somewhere around 1984?
You can read his posts over on roadbikereview.com He's posted as "spokesniffer".
Some Specialized history