Joseph Smith, Jr. seems to have gotten in a rut with a minor obsession for using “forty and two years.” He mentions it four times in the space of only 44 verses. It also appears earlier, in Mormon 2:9.
Ether 9:24 And it came to pass that his wife died, being an hundred and two years old. And it came to pass that Coriantum took to wife, in his old age, a young maid, and begat sons and daughters; wherefore he lived until he was an hundred and forty and two years old.
Ether 10:8 And when he had reigned for the space of forty and two years the people did rise up in rebellion against him; and there began to be war again in the land, insomuch that Riplakish was killed, and his descendants were driven out of the land.
Ether 10:15 And it came to pass that Levi did serve in captivity after the death of his father, for the space of forty and two years. And he did make war against the king of the land, by which he did obtain unto himself the kingdom.
Ether 10:32 And it came to pass that Com drew away the half of the kingdom. And he reigned over the half of the kingdom forty and two years; and he went to battle against the king, Amgid, and they fought for the space of many years, during which time Com gained power over Amgid, and obtained power over the remainder of the kingdom.