What is the justification against differentiating between short and long journeys concerning lot selection?

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The justification against differentiating is that if the husband travels with one wife based on the lot, the situation is judged like a long journey, not a short one. Furthermore, if a short journey were treated as residence, it would not be permissible for him to travel with one wife and not the other, just as it is impermissible to grant one wife a period of intimacy (Qasm) exclusively over another while residing at home.