After marrying again, how long does the husband devote his nights to the new wife before the rota begins?

The sunnah gives the new wife several consecutive nights first, before an equal cycle of the rota (turn of nights) begins. The Prophet ﷺ showed this practice: “when a man marries a virgin while he already has a wife, he stays with her for seven nights, then divides the rotation” (Sahih al-Bukhari 5213); for a previously married woman (janda), three nights. These opening nights are the new wife's right and do not need to be made up to the existing wife. After that period, begin a fair cycle among all. Inform the existing wife early so there is no misunderstanding or feeling of being left out. If your household situation is complicated, refer to the religious office for specific guidance. See the rota in practice.