When did they leave the street?

[AmazingMumford]

Now I have asked people this question before, but Iv'e never gotten an exact answer. But I see that there are many new people here who watched Sesame Street in the 70's and 80's so mabye they will know. When exactly did Cookie Monster, Grover, Ernie and Bert stop appearing in street scenes and street stories? By the looks of things on Noggin I'd have to say 1979. Although David did mention Cookie Monster and Grover in the Star Wars episode from 1980, then again that doesn't necasarily mean they were being used in street scenes at that time. I'm guessing it had to be some time in the very early 80's or the very late 70's, but I just don't know because Since Noggin was only 67 Sesame Street episodes from 1969-1989 It's hard to say exactly when they stopped appearing on the street. But anyways I know that Ernie made a Comeback in the year 2000, and Grover Cookie and Bert gradually made their way back over the next 2 years. So does anyone know the anseer to this?