"long preparation" is a correct and usable phrase in written English.
Example: After years of long preparation, the team finally won the championship.
"We had a pretty long preparation camp, a too long preparation time.
Hundreds of actors and long preparation went into the festivals.
Mr. Maro described the long preparation of his protégés and their recent creative efforts.
"Life is a long preparation for something that never happens," Yeats warned.
During the very long preparation, I get to know the actors, and it creates a climate of mutual trust.
Long preparation, therefore, preceded her act of defiance.Yet life in the South became too hard for her after the boycott.
In 933, after long preparations, Henry routed a Hungarian attack on Saxony and Thuringia.
The other patron is Joachim Gauck, who became the president of Germany in March, too late to be involved in the long preparations.
In his 1650 account to the senate of the Republic of Venice Petar Parchevich described the long preparations for an armed struggle and the support-seeking visits of his fellow townsmen to the kings of Poland and Austria.
Many people scoffed at our months-long preparation for the release of "Phoenix".
The only true missteps were a duck confit that, despite careful days-long preparation, came out dry and stringy, and a tuna tartare that, though fresh, had an odd, gelatinous texture and an acrid aftertaste.
