If someone feels strongly that EM (or most any single investment) is overpriced, or gone up too much, then I don't think it's a big deal to just not buy it. So long as you won't change your mind should it double in a year. And your asset allocation without the item is reasonable. (I think a portfolio without EM can be reasonable.)
About a year or year and a half ago, I looked at REITS, and thought they deserved an allocation in my portfolio. But, wasn't willing to buy in at those prices.
I still haven't bought, and won't, until they seem reasonably priced to me.
On the other hand, when VWO came into this world, EM had already gone way up. I bought it, even though it already had quite a run. It didn't seem overpriced to me, but I've said that before about EM, back in 96/97.
I dont' sweat the ones that "got away." There's been several things I almost bought, that then went up to the sky, but I've done fine without them. Besides, I would have sold early anyway.