Western Airlines pax also got lifetime comped by Delta if they had lifetime before. In the old days Flying Colonels had lifetime as well, but that was then abandoned.

There was however a cut-off at some point. I had a lifetime on Pan Am and it wasn't carried over. I didn't expect it to be. Many years later I learned on FT that this perk did exist and contacted Delta, they basically told me that the books on this were "closed" after five years and they no longer maintained the old records.

FT had something to do with the Ambassador club thing as AA monitored all the "chatter" about buying it and getting AA lifetime.