We feel as though it would be unfair for another player's time with the same character to count toward a current character's residency length, so we're going to have to say no here.

That said, length of time in Luceti is not the only measurement by which John will select his journal bearer - it's not like someone is automatically more trustworthy just by virtue of having lived in Luceti for years and years! It just means that he's had more time to observe the person in question and is better able to make a judgment.