I agree with most all of the points raised here, and have brought up many of the same things when proposing good candidates for calendars to hold through earnings. As Kim mentioned, we use several sources to identify stocks that have a history of staying within implied move on earnings. The one statement that I would disagree with is " If IV is compared to anything other than it's OWN history, it has no meaning. " While it is important to know a given stock's IV history so you have a good indication of what the post-earnings IV drop will be, IMO the IV in general does come into play in two major ways with these calendars you hold through earnings:
The higher the pre-earnings IV, the more of a post-earnings move that can be tolerated and still have the calendar be profitable. The IV differential between the short and long legs is important too - but you'll almost always see a decent sized differential when you short leg is expiring the same week as the earnings announcement. A stock with a lower pre-earnings IV% will see its calendar value go close to zero post-earnings on a much smaller stock price move than stocks with much higher IV%.
The higher the pre-earnings IV, the higher the max gain percentage on the trade if the stock winds up near your strike. Stocks with high pre-earnings IV can have their calendars make 200%+ if you hit the strike and its late in expiration week, mid-level IV stocks can make around 50-100%, but for lower IV stocks your max gain is much less - and for a cheap 0.10 to 0.30 cost calendars, the 0.o3 typical round trip commission to open and close makes up a significant percentage of the calendar cost and will consume a lot of the profit.