An iron condor is 4 options (two verticals). Every option in this spread is either priced above fair value, at fair value or below fair value. Over an infinite number of trades, the only way this strategy can produce a positive expectancy is for the trader to consistently sell each option above its fair value and to buy each option below its fair value. Anything else will produce a negative expectancy. There is no way around this. The argument is often given, Oh, I'll adjust it. But the adjustment is a whole other trade and that trade itself has to be executed at better than fair value prices or it too will have a negative expectancy. There is no mathematical way around this. Why it sells on the seminar circuit because it's easy to teach, it's great for lazy people who don't want to put any effort into trading and it's perfect for guys that are scared to take a directional view. The problem is it just doesn't work.
Of course it works for awhile, until it doesn't. One can put on an iron condor in GOOG if they think the two component verticals are trading above fair value. Selling the verticals in this example should produce a positive expectancy if the trader is correct on their volatility assessment. But that is not how guys are taught to trade it. They routinely put it on an index usually every single month on the same day of the week even and then sit back and pray and hope the market doesn't go anywhere. Trading is 1000 times harder than that. Time does not matter (Comparing weekly iron condors to monthly). Negative edge is negative edge. You can't manipulate negative edge into positive edge through time or adjustments. You simply need to have a volatility edge to make the trade. Just slapping them on every week is not going to make you money and why should it? Markets don't just give money away because you have the ability to use a mouse.