Sitting on our tenure and promotion committee, I'd be extremely skeptical about someone having 30 graduate students doing a good job supervising them, and we consider having a lab of 3-5 students to be fairly productive for a pre-tenure faculty member.
I think the causation is reversed - if you're successful enough at writing grants, which involves convincing your peers that your research is that good, to support 30 graduate students, you've already met the qualifications for tenure which involves convincing your peers that your research is good enough to want you in their department for as long as possible.
I think the causation is reversed - if you're successful enough at writing grants, which involves convincing your peers that your research is that good, to support 30 graduate students, you've already met the qualifications for tenure which involves convincing your peers that your research is good enough to want you in their department for as long as possible.
Personally, my work load is worse post-tenure.