I have only taken a river cruise prior to my Ocean cruise last week. I was unaware that Viking offered an Onboard Booking bonus on booking another cruise (Ocean or river). I booked an additional river cruise for 2026 a few weeks prior to departure. You cannot take advantage of the program, nor can you cancel and rebook. I was told they would take the Onboard booking credits away from your reservation. Wish I would have known this program was available, as it was not on the river cruise. Major disappointment. Wait until you are onboard to book. Seems the credits were quite nice.