Multi-year deals are a buyer-driven convention that vendors accept too easily. They underestimate what they're giving up. In this article, we examine exactly what is being conceded, the opportunity cost and sticky-product math, the single rule that is worth more than any other negotiation tactic, and how to price a multi-year deal correctly for the instances where these deals make sense. Plus, a look at the deal structures to avoid, and why vendors who treat the multi-year contract as a "set it and forget it" arrangement get hit hardest in year three.