The number forty-two is mentioned frequently in the Book of Mormon—some of which are found in the book of Ether (9:24; 10:8, 15, 32). Ether 10:8 states that “[When king Riplakish] had reigned for the space of forty and two years the people did rise up in rebellion.” Verse 32 mentions that Com “reigned over the half of the kingdom forty and two years.” Many things were recorded as having happened in multiples of forty-two. This may reflect some feature of ancient calendaring patterns and information recorded by ancient astronomers; but as intriguing as this may be, we cannot be sure.
Randall P. Spackman, Interpreting Forty and Two Years in the Book of Mormon, (Self-published article online: 2010–2011).