We're getting there
"Right now it is 1:40 am and my 3 day-old son is finally asleep in my lap"
Well first off, congrats on the birth of your new son! You shouldn't be discussing obscure FARs with me at this time!
Thanks to my trusty IFR Magazine subscription (and the recent FAR reviews I've had to do b/c of this thread), I'm quite familiar with cruise clearances and through clearances and what have you.
Regarding through clearances, Singlecoil wrote "You won't find that one in the regs either."
Singlecoil, at least challenge me. YAWN.

It's 7110.65 4-2-6 (the controllers' manual).
By the way, the references for Cruise clearances are AIM 4-4-3 & 7110.65 4-5-7, and contact approaches (another obscure one thrown down) is 7110.65 7-4-6 & AIM 5-4-22. I'm quite familiar with all of them, though I'm sure many of the board members are not. I'll post the references to the elusive one that covers approach clearances allowing en route descents if I ever find it
So, now to the subtle nuances:
"If the controller says, "Cleared for the VOR 7 approach Sheeptown airport." You woud read back, "Cessna 65C roger, cleared for the VOR 7 approach Sheeptown." Whenever you decide to descend, then you must also report leaving 8000 feet. That is what I was referring to about reporting leaving the last assigned altitude."
If ATC did not ask you to descend (and remember, I'm still maintaining that they have not authorized you to descend), then you don't have to report jack to ATC. In my case, b/c I'm not descending (yet). In your case, b/c AIM 4-4-9d doesn't mention anywhere about reporting anything to ATC, only that you must descend "at an optimum rate". AIM 4-4-6b, the read back rules, states that pilots should read back "those parts of ATC clearances and instructions containing altitude assignments or vectors as a means of mutual verification." Now, I would argue that ATC didn't clear you to descend in the first place b/c they DIDN'T mention any altitude in your "Cleared for the VOR 7 approach Sheeptown airport". Even if I'm wrong about the approach clearance being an allowance for an en route descent, you still are not required to report leaving an altitude here (you would be in your second example of "Cruise Sheeptown 8000" if you were permanently vacating 8000, of course).
Assuming I'm correct on the en route descent not being part of an approach clearance (just go with it, for the moment, since neither of us can actually site a reg. here), how have pilots been able to continually descend to Sheeptown, despite not having a clearance to? I would say that we were unknowingly using AIM 4-4-1b, which says "If a pilot prefers to follow a different course of action [i.e., leaving their assigned altitude to get down for the approach, which is perfectly understandable] the pilot is expected to inform ATC accordingly." So, we tell ATC that "Cessna 65C is leaving 8 for 4." ATC, who couldn't care less (nobody's anywhere near Sheeptown but you) knows why you're going down, where you're going to, and has no problem with it. Furthermore, they are not required to read back your self-amended clearance unless they have an issue with it. So they say nothing, you descend, and everything is covered by the AIM. Maybe?
See, this whole situation only happens in sparsely populated airspace, so we'll never know based on experience what's going on. Normally, ATC would clear you for the approach and give you a descent to 4000. You read back the 4000 (which you "should" do (AIM 4-4-6b), but are still not required to, by the FARs or AIM at least)), and then you drop down to the 3,500 MOCA w/in 22 nm of the VOR, then go shoot the approach. This scenario is totally covered by the FARs and AIM. If you leave out the descent clearance, than that's where it gets hairy.
In short, there is compelling evidence in the FARs, AIM, and 7110.65 that an approach clearance is NOT a clearance to descend on an en route segment, but there is plenty of anecdotal experience from flying that, if you report leaving your assigned altitude, you can go down to the MEA and subsequent MOCA w/in 22 NM after hearing your are 'cleared for the approach.'
End result, you can descend and ATC likely won't care, even if they didn't clear you to (which is unresolved). But, this is a FARs discussion, so the answer has to be better than that for me.
"It is an excellent question to ask on an interview because it is a test of practical knowledge, not just book knowledge.
By the way, crow isn't served here, only humble pie, and I've had several servings on flightinfo.com."
I've got my piece of pie selected, but I think someone else should too. There's no resolution on this issue as far as I can see . . . yet.
-Boo!
Who would have ever though 'Checks' simple post could get so difficult? I'm thrilled to see that this thread hasn't wandered off topic, and has remained a civil discussion