Lengthening doctorate and post-doctorate training allow science, technology, engineering, and mathematics (STEM) Ph.Ds. to persist in high-intensity academic research environments at the cost of significant lifetime earnings. Using the largest longitudinal survey of U.S. Ph.D. recipients, I construct career paths for 135,599 STEM research doctorate holders over six job types and two employment statuses. Examining Ph.D. cohorts in four major STEM fields from 1950 to the present, I find evidence that the increasingly prevalent postdoctoral position allow STEM Ph.Ds. to remain in high-intensity academic research positions, albeit not necessarily on the tenure-track. However, these research opportunities come with an approximately $3,700 deduction in annual earnings per postdoctoral year. Taken together, STEM Ph.Ds. must weigh the non-pecuniary costs of remaining in academic research with this earnings loss to determine if postdoctoral positions are a worthwhile investment.