I principally use my H24 settings (4.8GHZ, no PLL, 1.37v, 2133MHz) for testing BIOS and old one seems to work better than the newz.
For 5.4 GHz benchable, I'm at 1.60v (1.615 max I did but no more winning results) .
You think the chip can be degraded and need more voltage with time ?