Helium mass fraction Y versus the empirical (unclumped) mass-loss rate relative to the stellar mass (Ṁ/M) for our sample stars with their respective 95% confidence intervals. Added to this is the set of very massive luminous O, Of, Of/WN and WNh stars analyzed in Paper XVII, excluding the nine stars in common with this paper. Also shown are evolutionary tracks by Brott et al. (2011) and Köhler et al. (2015) for stars with initial spin rates of approximately 200 kms^-1 (upper panel) and 300 kms^-1 (lower panel) with dots every 1 Myr of evolution. These tracks are truncated at 30 kK, which is approximately the temperature where the stars evolve into B-type objects and thus are no longer part of our observational sample.