At Harvard, sequential appointments are less common, but the timespans have lengthened. They aren't in it for the money. Health insurance for postdocs, like so much of their lives, depends on the mentor who runs the laboratory. The federal government wants postdocs to be 'unfettered,' so it does not allow us to treat these people as employees. This cuts them out of participation in Harvard employee benefits.
Modern science is supported by research grants focused on specific proposals.
Postdocs are on the firing line. They have to make sure the lab research gets done. Under these conditions, professors often depend on postdocs to run their labs, which might include 20 graduate students and as many as eight or nine postdoctoral fellows. The faculty mentor flies around the world, giving talks and raising funds, while the postdocs carry out the daily hands-on work of science. Yet there are also sad stories.