It depends on the amount of technical debt in the project. When there's no technical debt, sure, grad students are the backbone. They can happily go about thei

It depends on the amount of technical debt in the project. When there's no technical debt, sure, grad students are the backbone. They can happily go about their projects and supervise undergrads, while the postdocs supervise them and apply for jobs. In a place where there's a lot of technical debt, a postdoc is going to be far more productive than a grad student. In some experiments many grad students spend years floundering around before they learn enough to cut through the cruft and do real research. It's pretty silly to fire all the postdocs just when they've managed to understand everything and replace them with new grad students. The tricky thing is keeping enough of the technical staff around, and coming up with a system where they are rewarded for eliminating debt, rather than penalized for making their own hard-earned skills obsolete.