I read this thread and the one you linked to before posting and they make good points about how being near the market high isn't a reason not to buy, but I didn't see mention of p/e. Maybe I missed it.
You say "if you do see a big drop feel free to take advantage if you've got a way to but don't sit around in cash waiting for the drop." That sounds to me like you agree that sometimes you might want to tweak your buying pattern slightly, even if the overall strategy is close to periodic buying for DCA. No?
I say feel free to take advantage if you have a way. I view it this way. You have a cash flow of X. You have spending of Y and savings of Z. For some people they could recognize a market drop and reduce Y for an increase in Z. I'm not advocating putting Z into cash and wait for drops. That is a losing situation.
If you've got proof that PE timing works long term then please bring it.