[gww]

One point that I seem rarely mentioned especially in the life sciences is learning when to tell your mentor that you have enough to leave. In my experience a lot of labs will try to keep their senior PhD students around as long as they can because they don't have a suitable replacement and they are cheap labour. I know people who stick around for 6 to 10 years to chase after a high impact paper (that doesn't often manifest) or they can't let their work go and pass it off to someone else, or in the very malicious cases the PI won't let them go until they publish another paper etc. The department I was in was determined to get the average PhD down to less than six years but still hasn't reached that point.

The trainees supervisory committee is usually there to push them out but in many cases they also have a close relationship with the PI and aren't going to force a productive student to graduate. Those extra years are rarely useful for their overall career prospects.

I think students need to be aware of when they should draw the line and move on. Spending three more years in their PhD probably won't pay off nearly as much as three years of accumulated experience in industry job or in a post doctoral fellowship in a new lab.

[lambdatronics]

Yeah, I have seen instances where it's the student's lack of drive/progress, the PI being unreasonable, the student's project was too ambitious, plain bad luck (lab equipment caught fire & destroyed), or time taken off for family considerations (child-birth, caring for ailing parents).

I graduated in 6 years (including 2 years of coursework), which was the mode (not the median, though) for my department. The distribution skewed to the long side, and 5 years was the shortest I can recall.