When is ghusl (ritual bath) from menstruation obligatory if the bleeding continues for more than ten days, given that the natural duration is five days, and does the insertion of a copper IUD affect the duration of the menstrual cycle?

The IUD often increases the days of menstruation and makes it irregular. If a woman's customary period changes and the bleeding continues beyond her usual duration, she is considered in menses as long as it does not exceed fifteen days. However, if the bleeding exceeds fifteen days, she is considered to be experiencing istihada (prolonged non-menstrual bleeding), and a woman in istihada may fast, pray, and engage in marital intimacy.