I think a 7-12% correction would be far more healthy. But I do agree that if this thing keeps going this could turn into a 20%+ selloff at some point. All is just my opinion, and I could always be wrong though.
I think a 5 to 10% correction would be better .... we recently had a 3% correction and that was insufficient to squeeze out the excesses and create a healthier market .....
But the sense I'm getting is that the market is going higher before it goes lower .... it has lots of momentum and complacency is evident by the very low VIX index. Every little dip gets bought. I'd guess it will be at least several weeks and perhaps months before we finally get hit with at least a 5% correction. The higher the market goes, the harder it will eventually get hit.