Here is yet another example of a subtle detail that could easily get mixed up and present a glaring inconsistency in the Book of Mormon:
In Mosiah 1:1 we learn that King Benjamin had "continual peace" for the remainder of his days. He decides to pass the kingship along to his son, which he does, and according to Mosiah 6:3, he lived three more years and then died.
In Mosiah 7:1 we learn that his son, King Mosiah, had "continual peace" for the first three years of his reign.
Each of these verses is referring to the same three years.