OC and EIST C1E

I know that there are some threads about this subject (if not many), but none that I found seem to answer my questions.

I am fairly new to overclocking, and I'm now starting to gradually test some OC on my new rig.

I have an ASUS P7P55D-E Pro board with an i7 860 processor. Also got some OCZ Gold Ram at 1600MHz with 8-8-8-24 timings.
I think I'm starting to understand how to OC, the only thing I keep wondering is the following:

Everybody turns of Speedstep en C1E for OCing, which is understandable, because it's easier to test, or some people want to run folding 24/7. But what I wondered was, if I settled on an OC profile that I'm pleased with, can I turn Speedstep and C1E back on to save some power and prolong the lifespan of my processor (less volts at idle)?
Or is it unsafe, because at the lowered voltages and me suddenly asking 100% load from the cpu, it might get unstable there and freeze up (because for a plit second it doesn't get the voltages to backup the increased multiplier and thus overall speed?

Same question with the TurboBoost technology, is it safe to leave it on, so it can shut down 3 cores and boost 1, or will it easily get unstable too?