Do you have any examples of this ?
What would be the point of running at full speed, when not running some program like Folding@Home ?
At higher multipliers it may be necessary to run it 24/7 with fixed Vcore and power-saving features disabled.
I have gotten my 2600K to work at 5GHz with offset voltage and power-saving features enabled. However, the Vcore was higher than I'm comfortable with, and I wasn't convinced of the stability. The instability comes for most people at these high OC's due to the Vcore not responding fast enough to load changes or dropping too low at idle. A robust VRM on the motherboard should help, though.
Power-saving features are definitely feasible at slightly lower multipliers. My usual OC is at 4.7GHz with Vcore at Normal and DVID (offset) at +0.070V. This is with Turbo, HT, and power-saving features enabled (EIST and C1e).
Currently I'm at 4.5GHz because I'm folding. There was nothing wrong with the 4.7GHz settings, but the heat this month has been oppressive. My CPU is under water now, but even so it was hitting mid-70's C at x47. Dropping to x45 dropped the temps to the upper 60's.