[zahlman]

Given that the market has moved so strongly away from dividends in favour of stock buybacks and other reinvestment (i.e. the successful companies are now much more often "growth" companies rather than "value" companies), and given e.g. Buffett's wisdom about total return, I don't know that traditional rules of thumb about P/E make sense any more.

[impossiblefork]

In the end the value is just discounted dividends or there's an arbitrage opportunity under the risk neutral measure.

This isn't a matter of rules of thumb. This is what's required to have prices that do not create an arbitrage opportunity.