However, in almost all of these benchmarks and code comparisons, the same challenges and discrepancies keep re-appearing, and may continue to be “re-discovered” through future benchmarks. Therefore, this presentation is an effort to document such similarities and valuable lessons learned from these exercises so that future verification studies can focus on comparing more advanced capabilities and features rather than on these expected fundamental differences. The author presents some of the key lessons that he has observed through his participation in various code comparisons and benchmarks with the goal of stimulating discussion and encouraging the community to be aware of expected differences between codes. Some of the valuable lessons to be discussed include: 1) most of the differences in code results were not due to different code algorithms or calculation approaches, but due to different interpretations of the input specifications among the analysts, 2) the first specifications will almost never be the final version and will almost always require being iteratively updated with preliminary results from codes, 3) different codes often report or account for mass inventories at different times within a given year or even time-step that often lead to differences that are misleading, 4) for more complex scenarios, all codes may need to make approximations at one level or another (in the input or modeling of mass flows), and others.