Well, hopefully the folks doing a PhD are the ones that "want to just do research". I am doing my PhD now and I feel like 3 years (on top of a two-years masters

Well, hopefully the folks doing a PhD are the ones that "want to just do research". I am doing my PhD now and I feel like 3 years (on top of a two-years masters) is not enough time for a quality dissertation. It is enough time for at least one good paper. But to avoid mediocrity, I think it can be useful for students to actually slow down (design thoughtful experiments, reproduce what others have done, thorough literature review. etc.) instead of rushing against the clock. Sometimes there is a negative attitude toward students who ask for program extensions. "Oh, you weren't able to finish in three (four, five) years, so you must not be a good scientist." Something along those lines. But there shouldn't be.