April 4th 1971 - The final episode of "Hogan's Heroes" aired

"Rockets Or Romance"

Hogan and a beautiful underground member are teamed in an attempt to locate and immobilize three mobile rocket launchers.

Hogan's Heroes did not change a whole lot over the course of its run, in my opinion. For me, just catching a random episode, it's not always easy to tell if it's from an early, middle, or late season...! About the best giveaway is the length of hair for some of the men (especially sideburns!), as far as knowing right away how old the given episode is.