Is it obligatory for the husband to divide the days between the two wives, or is justice ensured by the second wife's consent that her husband spends certain days with her while she is in another country?

It is permissible for the wife to agree with her husband to waive her right to spend the night (mabit), and suffice with meeting him at specific times or days. In this case, he is not obligated to be just or to apportion nights for her, because she has willingly relinquished her right. This is because the right in this matter belongs to both of them and does not extend beyond them.