Following the surge in the lithium market in 2015, there was a notable rise in the design and construction of spodumene concentrator plants in Western australia. These facilities utilised conventional, well-established unit operations and were developed by experienced industry service providers. However, many plants failed to meet projected metallurgical performance, with numerous facilities unable to achieve targeted lithia concentrate grades and recoveries. This underperformance justifiably led to caution in approaching subsequent project development with a view there is significant inherent process risk involved. This paper explores the impact of failing to apply critical flow sheet development principles, such as metallurgical test work definition and result interpretation, in project development phases. We investigate how these factors contributed to the disparity between expected and actual plant performance. Case studies are provided comparing expected performance with realised performance, and we quantify the economic impact of the underperformance. additionally, this study examines how perceptions of these operational failures, particularly among stakeholders in the investment sector, influence the broader industry perspective. Leveraging insights from these learnings, the paper will provide guidelines for the flow sheet development and execution of projects within the critical minerals space. Ultimately, the paper aims to offer insights that can guide future metallurgical test work planning, enhance process risk management, and improve execution strategies, contributing to more successful outcomes in critical mineral concentrator projects.