Assuming the assinine form he has to live for ten years. After that he is born as a crocodile, in which form he has to live for a year. After that he regains the human forin.
गर्दभत्वं तु सम्प्राप्य दशवर्षाणि जीवति। संवत्सरं तु कुम्भीरस्ततो जायेत मानवः॥