Temporary decrees and absolute decrees basically speed up court processes. Courts have to give specific time frames for cases or things will never reach a conclusion. Decrees do that by giving a time frame in which the decision may be changed with new evidence or applications in regards to the case. But if these are not produces within that time frame, then the decree becomes final.
Of course, it is possible to request the case to be reopened or retried if new evidence were to come up at a later time. But for cases where new evidences are not found and everything remains the same, the court saves time by issuing the decree and moving on to the next case.