I think 2 or 3 debates are needed at the most. If you haven't gotten your point across by then, you never will.
I mostly agree but would put it at 3-4.
What's missing from these contests is an outcome or resolution. And they are contests. Each participant is pitting their oratorical skills and reasoning ability against another. At the conclusion of each contest there are clear winners, but no elimination, and therefore no resolution.
It's nice that we gave Huntsman and Paul a chance to speak their peace......now go away and let us concentrate on serious candidates. The interesting thing is, depending upon how you scored each contest Rick Perry and Michelle Bachman would also be gone. Would that be a good thing or a bad thing at this point in the game?
On the plus side, having several opportunities to debate has broadened our chance to see these guys peek outside of canned speeches and ads. One of the missing aspects is the thoroughness of examination. I hated Mrs. Goldstein's ninth grade math class because it wasn't enough for her to press you for an answer - she made you show your work. She insisted on an explanation of how you arrived at your answer. Which meant that you couldn't guess or make wild guesses. She insisted on not just the correct answer but the right answer and we were better students for it.
Likewise, we got to hear Perry's soundbyte on immigration but not an explanation on how he thinks it could possibly ever work. Or how Paul's isolationism would fare on 21st century Earth.
(It's time to try out my latest metaphor)
So far what I've seen of the candidates on display in these debates shows Gingrich as a magnificent diamond - complete with flaws, Cain as a diamond in the rough, Perry like an industrial-grade diamond - useful enough but nothing you want to give your sweetie, Romney as a Cubic Zirconium - an excellent presentation but at the end of the day still not the real thing, Paul like Pyrite (better known as Fool's Gold), and the rest minor gems.
They all have their strengths, they all have their weaknesses. All are imperfect but even the least of which stands head & shoulders above the miserable wretch currently doing his "Occupy White House" imitation.