A common assumption in the social stratification literature is that the lion’s share of people reaches occupational maturity quite early in working life, i.e., they end up in an occupation/class position and stay there. The conventional view is that career maturity is reached around the age of 35. By using Swedish longitudinal occupational biographies across six birth cohorts from 1925 to 1984, this study challenges this view. Our findings reveal substantial career transitions throughout working life, an increase across cohorts, and a wide variation in the age of the last class transition. This suggests that careers are not in general static positions from a certain age, but fluctuate over time. There are signs of a general slowing down of career transitions across working lives, but this comes later in life and to a smaller extent than expected. These findings suggest that research often based on cross sectional data, e.g. studies on intergenerational mobility and class differences in health, need to incorporate career mobility data. More research is needed to illuminate if the results of Sweden, in terms of a low and decreasing level of occupational maturity can be replicated in other countries.