So, after a brief period in the late 1960s and early 1970s when he replaced the monologue with a fictional one involving "multicolored rainbow roaches", he decided to do it only on special occasions from that point forward.
Following a short time in the late 1960s and early 1970s, during which he replaced his monologue with a fictional one involving "multicolored rainbow roaches," he decided to use this narrative exclusively for special events thereafter.