use-by date
idiom. A metaphoric date after which something is considered to be outdated or no longer applicable. Also: use by date.

Example Citations:
But the novel, though finished, was never submitted to a publisher. It needed a second draft but that gave way to the demands of a full-time job and family commitments. Eventually the theme, terrorism and women's liberation, reached its use-by date.
—"Bill finds himself beached in the best possible way," The Advertiser, February 13, 2004

This week Philips, the huge Dutch electronics company that invented the cassette and technology that led to the CD and DVD, announced the closure of its remaining VCR production lines.

Philips conceded the decision would cost it sales. People were comfortable with the technology, a spokesman said, but Philips believed it had reached its use-by date.
—Garry Barker, "Will Video Be Killed By The Rising Star DVD?," The Age (Melbourne, Australia), February 12, 2004

Earliest Citation:
The Prime Minister, Mr Hawke, made it clear yesterday that he was prepared to break promises again — but added that he did not expect he would have to do so.

He was asked at the National Press Club whether he could give a "use by" date on his promises in future.
—Mike Steketee, "I may break word again, says Hawke," Sydney Morning Herald, July 9, 1987

On a perishable food product, the use-by date is the date after which the item will no longer be fresh. This is also called the best before date, and that phrase, too, is being used idiomatically:

Prime Minister Paul Martin's promise to tackle the "democratic deficit" in our country looked fresh for a minute, but it should have been stamped "perishable goods."

Just a handful of weeks ago, Martin, then in the midst of the Liberal leadership race, acknowledged too much power was centred in the Prime Minister's Office (PMO) and urged that individual MPs be allowed to vote on behalf of their constituents and consciences rather than slavishly toe the party line.

He also acknowledged a need for Parliamentary vetting of nominees for appointment to the Supreme Court of Canada. Now these and other similar pledges, having passed their "best before" date, are effectively being tossed down the toilet.
—"Paul's one-man show," The Calgary Sun, February 8, 2004

Thanks to Bob Pedersen for passing along this phrase.

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