Stephen King first came up with the idea for Under the Dome in the 1970s, but didn't complete it until decades later, finally publishing the novel in 2009 and now enjoying a successful debut of his series on CBS (13.1 million viewers tuned in for the first episode, an incredible number for a summer program). Imagine if King had never returned to that adventure -- his creation would have ended up locked away in the recesses of his mind, like the small town of his novel, trapped in an invisible, impregnable force field bubble, never to be enjoyed by others.
Likewise, when King first published The Stand, his epic was trimmed down, key scenes were omitted, and characters were discarded. Luckily, he saved those ideas, years later releasing a massive, expanded edition, which became another bestseller. Those additional scenes with Trashcan Man, etc., have become fan favorites and were also included in the popular TV mini-series. Imagine again if King had just chucked those unused portions of his original manuscript, destroying them forever?
I've mentioned before in my article "How to Beat Writer's Block" that old ideas can be salvaged and later repurposed. I'm still working on plots and still tweaking characters I developed when I was a kid. Some of those ideas will never see the light of day, but others might. Why give up on the possibility that there might be gold in those originally flawed or unpolished words? There could be a good story or two still waiting to be told, waiting for the right time to be dusted off and shared with the world.