This is terribly field-dependent. In nursing, it's not uncommon to see female candidates move out of their postdocs into a PI position in their mid- to late-40s, and even early 50s. Why? They've already had one career as a clinician before they entered a PhD programme. In addition, they may have taken one or more mat leaves.
Yup, true in education as well--although more typically the move is made in the early 40s. I think this may be the pattern in a lot of professional fields.