'has been stale' is correct and usable in written English.
You can use it to describe something that is no longer fresh or appealing. For example, "The bread has been stale since yesterday."
With Harris struggling, the Nets' bench, a productive crew throughout the postseason, has been stale against the Lakers.
That deal enabled the company to focus on merchandise like pots and pans, the market for which has been stale in recent years.
Local journalists in Bangladesh have reported that not all promised aid has reached the hungry, and that some of it has been stale or rotten.
The company's ballet master in chief since 1983, he has demonstrated more aspects of ballet-making technique than most choreographers will ever learn, and yet for decades now most of his new work has been stale: lacking either felicity of invention or stylistic individuality.
This is childish and myopic, and it speaks to the intellectual void at the party's center that the most Democrats have offered the peace process so far is hysterical rhetoric about North Korean leadership that has been stale for upwards of 25 years.
Sporting a 20 mpx Sony IMX269 sensor, a high-quality 3-inch touch-screen and a raft of sharing-friendly features, it's crashing into a space that has been stale for a while.
On a slightly different topic, most war Hollywood depictions for the past 25 years have been stale, formulaic, and utterly star driven.
He might have been stale because his previous appearance was July 9, when he gave up one run in seven innings in a 6-1 victory at Seattle.
Musical biopics have been stale for years, or at least since whenever Walk Hard came out and eviscerated the entire genre.
What might have been stale minimalism are instead geometric sculptures with crisp, unwavering lines, brought to life with the introduction of the (nearly) living either taxidermied animals or the artist's own physical performances.
