I’m pretty sure you can buy the SS onboard, but I don’t believe that Viking would prorate the SS package if you bought it a few days into your cruise. On CC and other sites I’ve seen Viking drink price lists. Why don’t you call or EM Viking Customer Relations to get optional wine lists and wine and hard liquor drink prices for your specific cruise, and then estimate your drink bill to see if the SS package would be beneficial to you. Also ask if the SS package is possible to prorate mid-cruise. Don’t forget that you can also buy a bottle in port and bring it aboard with no corkage fee. Although we had extra drinks on our cruises when we wanted them, it hasn’t been cost efficient for us to buy the package. Good luck!