Does a research/study have an 'expiry date' that prohibits it from being published in a journal after it has been completed?
Most research can be published even after many years. But if the research is out of date by then, the journal may not want it.
An example: I attended a lecture by Chinese mathematician Hua Luogeng sometime around 1980. He mentioned one of his earlier papers, giving the date submitted to the journal and the date published. Then he paused while we all noticed the 10-year-gap between. He explained that the "Cultural Revolution" fits in that gap, when all intellectuals were sent to work on farms in the countryside.