The Big Continental engines have their camshafts located below the crankshaft in the case. So, when stored for long periods of time, oil continues to drip onto the cam from the crank, making them (continentals) less susceptible to cam spalling when not flown regularly.
As Brian noted, however, I'd still run camguard in those engines.
The O-470 R model engine is about as reliable an engine as you'll find. It seems to be the preferred model of O-470, and the only one I have a lot of experience with. I think if you start off with a good one, and don't do anything really stupid, your chances of getting it to TBO are really good.
Shock Cooling: Engine experts have been saying for years that shock cooling damage is probably more a factor of re-using cylinders for many runs, instead of replacing them, rather than how pilots operate an engine.
There are LOTS of examples of flight training airplanes, which are generally operated regularly, and go from wide open throttle to throttle closed (or nearly so), with long glides pretty regularly. And, often in some pretty cold weather. Our engines all go to 500 over tbo, with this kind of abuse.
Start with a good solid engine core, and don't re-use cylinders that have been run through a half dozen runs. The metal in those old cylinders starts to work harden and crystalize over time, and then crack.
Now, PLEASE don't suggest that I'm saying you should abruptly reduce engine power, or otherwise abuse your engine, BUT, I think the engine manufacturers have now pretty well concluded that shock cooling doesn't apply to good engine components, and those old multi-run cylinders are probably going to crack anyway at some point.
So, reduce power judiciously, but I sure wouldn't spend a LOT of time in loooonnngggg shallow descents while worrying about shock cooling, especially if that long slow descent will put you lower than comfortable over hostile terrain.
MTV