Maintaining the business case during the project lifecycle involves regularly updating it to reflect changes and actual experiences such as incurred costs. This ensures that the project remains viable and aligned with business objectives, as part of the continual justification process. The business case is dynamically managed to reflect any changes in the project's environment and is a fundamental part of the 'business case theme' in PRINCE2.References: PRINCE2 7 Foundation source documents on business case management.

In PRINCE2 terminology, a dis-benefit is defined as a measurable decline resulting from a negative outcome. Dis-benefits are considered alongside benefits to assess the overall value and impact of the project.
They represent outcomes that are perceived as negative by one or more stakeholders.References: PRINCE2 Foundation Manual

User's quality expectations are documented in the 'Project Product Description.' This document defines what the project must deliver to meet the user's expectations, including the quality requirements and acceptance criteria for the final product, ensuring alignment with user needs and standards.References: PRINCE2 7 Foundation documentation on quality management and project product descriptions.

The Quality Register in PRINCE2 should record all quality activities planned and executed to ensure the products are fit for purpose (1), and the roles responsible for reviewing the project's products (4). This register helps in tracking and managing the quality review process effectively.References: = PRINCE2 7 Foundation handbook and online resources

The purpose of the Plans theme in PRINCE2 is to provide a framework to design, develop, and maintain the project's plans. This theme ensures that the project plans are aligned with the project's objectives and facilitate effective management and control of the project throughout its life cycle. References: PRINCE2 Foundation manual, PRINCE2 official resources