The phrase "long succumbed" is correct and usable in written English.
You can use it to refer to something that has been in decline, gradually reducing in strength, impact, or power over a lengthy period of time. For example: "The once-mighty empire had long succumbed to the forces of its enemies".
But they're doing it now, in 2012, with the rest of the N.B.A. having long succumbed to star player fever.
Each of those items has a powerful constituency behind it, however, capable of big-money pressure to which the Legislature and previous governors have long succumbed.
Tree root tentacles roam along crumbling cornices, winding their way around door frames and strangling the serene stone faces of smiling god-kings, oblivious to the fact that their empire has long succumbed to the natural world.
By now, his movie has long since succumbed to its own brio.
By contrast, only 17% of those with two long versions succumbed to the black dog.
The citadels of the established airlines long ago succumbed to the disruptive forces of budget operators Ryanair and EasyJet.
Balmain has long since succumbed to the lure of couture denim — but more recently, it was down and dirty with torn surfaces but ritzy ornamental effects.
At my parents' home, the magnolia in the backyard long ago succumbed to age and weather, the lawn is uninterrupted, and the neighbors' homes are safe from fly balls.
But by 1950, big roller mills had flattened the little stone mills (corn varieties themselves had long since succumbed to hybrids grown for shelf stability), and the era of uniform-size, flavorless grits and corn meal was off and running.
In a city where sports stadiums long ago succumbed to the lure of corporate naming rights and even the New York Public Library allowed a donor to inscribe his name on the marble facade of the flagship Fifth Avenue branch, the simple blue-and-white NY1 logo stood out for its seeming purity.
Blessed, or burdened, with psychic gifts, she reaches out helplessly to the world beyond — in particular, to her twin brother, Lewis, who, not long ago, succumbed to a heart complaint from which she also suffers, and which could fell her at any time.
