OBC that we receive from our TA is applied to the SSBP if you buy it pre-sailing or onboard.     There are other credits from Viking that do not apply to anything prior to sailing.   This is in Canada anyway.   But to answer the OP's question, in my experience there is never a deal, and in actual fact it can go UP from the published price when you booked to when you pay in full.   We used to get the SSBP on every cruise - ocean or river.  We don't any long