Historic selection for yield has improved the efficiency of dairy production for individual cows and current interest in direct selection for feed utilization aims to further increase productive efficiencies. However, herd efficiency will improve only marginally if selection practices reduce cow fitness levels and increase herd replacement rates. US genetic evaluations for productive life were introduced in 1994 and remain a robust general indicator of cow fitness levels. Productive life credits are limited to a cow’s lactation cycle with early lactation weighted more heavily than late lactation. There is considerable variation in herd-life with a genetic standard deviation of 5 mo despite a relatively low heritability (8%). Factors that influence herd life vary across herds and have shifted over time as herd management has evolved. The relationship of productive life with body size has become increasingly antagonistic over time, whereas the relationship with yield has gone from a moderately favorable to a low association. Given the current US Holstein population structure, productive life is strongly correlated with higher cow fertility and lower somatic cell score. Deriving the economic value of longer productive life is complicated by shifts in milk price, heifer rearing and replacement costs, and cull cow value. This has led to varying degrees of emphasis on productive life in different countries and across time. The evaluation of productive life is also complicated by the necessity of a cow’s life-cycle to be completed before her true productive life is known. Despite such challenges, higher sire productive life has been demonstrated to be associated with lower rates of daughter mortality and early lactation culling across a range of management systems. As dairy cattle breeders continue to emphasize productive and economic efficiencies, the need to consider traits related to cow fitness levels are of increasing importance to ensure that selection for cow-level efficiencies do not diminish productive efficiency at the herd level.