"decades thereafter" is a correct and usable phrase in written English.
It means "decades after that time" or "many decades later." Example: The researchers predicted that the effects of climate change would be felt for decades thereafter.
"Lady Chatterley's Lover" was, of course, revolutionary in its day, and for decades thereafter.
The play remained a favorite with amateur drama companies for many decades thereafter.
He thought Weill to be a "lousy teacher," but became his close friend and enthusiastic interpreter for two decades thereafter.
This essay will be discussed in the following section on the understanding and criticism of Hamlet because it influenced the Chinese interpretation of the play for decades thereafter.
For almost four decades thereafter, each new construction project was landscaped idiosyncratically, without any coordination with the rest of the campus.
That evolution, from its start and continuing for decades thereafter, has brought the school to its present place of global pre-eminence.
For decades thereafter, Cuba remained a virtual American colony, a period that Fidel has always referred to as the "pseudo-republica".
For decades thereafter, the former Vernon Valley/Great Gorge ski area was popular, especially among beginning skiers from the metropolitan New York area.
Spark focusses upon those who, in the immediate wake of the murder and for, possibly, decades thereafter, helped the murderer escape and supplied him with funds.
For decades thereafter, Likud alternated in government with left-wing coalitions, forming coalitions with minor parties, especially those with an ultrareligious or a nationalist ideology.
For decades thereafter, IBM sold more software than any other company (in 2004, its software sales totaled $15 billion, about 16percentt of its revenues).
