I’ve regrown the face hairs with 16.000 “Simulated Hairs” and no “Children Hairs” instead of previously 2.000 “Simulated Hairs” with 8 “Children Hairs” for each of them:

Hairs rendered as “3DCurves” with a “Root Diameter” of 0.2.
Cycles Render Time: 6 Minutes 44.33 Seconds.