After Walt Disney passed on in 1966, the Sherman Brothers viewed the song as his "theme song" because of his optimism and his visions of the future.
The Carousel of Progress was subsequently moved to Walt Disney World's Magic Kingdom, where it opened on January 15, 1975. However, General Electric requested that a new song be used for the show, so the Sherman Brothers wrote "The Best Time of Your Life" for this updated version of the show. General Electric ceased sponsorship of the Carousel of Progress in 1985, but "The Best Time of Your Life" was still used until 1993, at which point the show closed to be updated again for that park's New Tomorrowland. It reopened in 1994 as Walt Disney's Carousel of Progress, and an updated "There's a Great Big Beautiful Tomorrow" was again the theme song. Arrangements of "The Best Time of Your Life" and "There's a Great Big Beautiful Tomorrow" can be heard in the current background area music for Tomorrowland at Disneyland and the Magic Kingdom.
Meanwhile, at Disneyland, America Sings ended its run in 1988, after which many of the Audio-Animatronic characters were recycled into Splash Mountain and Star Tours, leaving the Carousel Theater empty. It would lay dormant for more than ten years, when a new version of Epcot's Innoventions was installed in it. "There's a Great Big Beautiful Tomorrow" was chosen as the theme song of Innoventions, with an instrumental version used as the area music and a lively rendition with new lyrics is sung by Tom Morrow (voiced by Nathan Lane), as a tribute to the attraction which originally occupied the Carousel Theater.