The 1874 RLDS edition changed “as long as” to “so long as”. This change appears to be accidental. Elsewhere in the text, there are three occurrences of “as long as” and seven of “so long as”, so either is possible here in Moroni 10:19. For each case, we let the earliest textual sources determine the reading. Here in Moroni 10:19, the reading “as long as” should be kept. The 1908 RLDS edition restored the original “as long as” to the RLDS text.
Summary: Accept “as long as” in Moroni 10:19 since this is the earliest extant reading, the reading in 𝓟.