Lifetime production is a key driver of the profitability of Merino flocks. While the genetic control and relationships between young and adult assessments have been evaluated previously, the conclusions have not been validated using data from a progeny test design, which extensively captures lifetime data from diverse sires and ewe bases. This paper estimated genetic correlations between lifetime age stages of greasy fleece weight, fibre diameter and body wrinkle, and between the traits. The results show that assessments for these three traits made at a young age have a moderate correlation (rg>0.6) with adult performance, however, they are genetically different from adult assessments. These results suggest measurement of adult performance is beneficial. Genetic groups derived from admixture analysis using genotypes provided a good alternative to account for population diversity when the pedigree-derived genetic groups are challenging to define accurately. Further work is required on the other important traits which determine lifetime productivity.