In Israel, the Jubilee was to happen regularly once every fifty years. In the rest of the ancient world, when a new king was crowned, he would issue an edict forgiving all old debts, enshrining new laws, and so forth. If you were a creditor in that world, you lived not knowing how long the king’s life would last. The Israelite system provided stability, especially when thirty or forty years still remained before the next Jubilee. While some have wondered if the Jubilee Year was only an ideal part of the law, something that only anticipated a future Messianic Law, I believe that at least some parts of the Jubilee Law were needed to be observed as a corrective for restraint of long-term indentures or debt servitude, for inflation, and other sorts of inequities.
Based on several phrases which King Benjamin uses, many of which can also be seen in the main jubilee text in Leviticus 24 and 25, a case can be made that Benjamin timed his speech to be given during a Jubilee year for the Nephites. This explains why Benjamin talks so much about not allowing slavery, about indebtedness and forgiveness, and why King Benjamin would go on to live and serve as a co-regent for three additional years after the coronation of his son. The observance of a jubilee would be an ideal time for such a solemn and thankful occasion.
Book of Mormon Central, "Why Did Alma Wish to Speak ‘with the Trump of God’? (Alma 29:1)," KnoWhy 136 (July 5, 2016).