According to the Agile Practice Guide, the product backlog prioritization is a continuous process that involves evaluating the relative value and urgency of the features or user stories that are planned for the next iteration or release. The product backlog prioritization should consider various factors, such as the customer needs, the stakeholder expectations, the market conditions, the technical dependencies, the risk exposure, and the feedback from previous iterations. Two of the most important factors that should be taken into account first are the cost of delaying some features against the business value they deliver, and the length of time each feature has been on the backlog. The cost of delay is a measure of how much value is lost or foregone by postponing the delivery of a feature. The longer a feature stays on the backlog, the more likely it is to lose its relevance, quality, or competitiveness. Therefore, the product backlog prioritization should aim to deliver the most valuable and urgent features as soon as possible, and avoid accumulating technical debt or waste. The complexity and the cost of development, the industry trends and the technical approach, and the reusing of components from another product are also relevant factors, but they are not the first ones to consider when reviewing and updating the product backlog priorities. References: Agile Practice Guide, pages 49-50, 54-55.