'Postdoc'

"An individual who has received a doctoral degree (or equivalent) and is engaged in a temporary and defined period of mentored advanced training to enhance the professional skills and research independence needed to pursue his or her chosen career path"

• Period of service: Postdoctoral appointments for a given postdoctoral researcher should total no more than 5 years in duration, barring extraordinary circumstances.
• Career Development: Host institutions and mentors should, beginning at the first year of graduate school, make graduate students aware of the wide variety of career paths available for Ph.D. recipients, and explain that postdoctoral positions are intended only for those seeking advanced research training. Career
• guidance should include, where feasible, the provision of internships and other practical experiences. The postdoctoral position should not be viewed by graduate students or principal investigators as the default step after the completion of doctoral training.

Some of the work now being done by postdoctoral researchers might more appropriately be done by permanent research staff, who receive the salary, benefits, and job security commensurate with full-time  employment. Such research staff positions are common in government, industrial laboratories, and outside the United States. The postdoctoral experience itself should be refocused, with training and mentoring at its center.

From a report from the US on the Postdoctoral experience