In the end it isn’t about money printing, interest rates, who’s president, stock buy backs, PE ratio’s, etc. etc.
It’s about whether a new technological advance is driving the bull, or low interest rates and money printing.
I would argue that the 2002-2007 bull was driven by low interest rates and money printing, thus not sustainable.
Since 2009 I’m seeing very interesting developments in transportation, renewable energy, bio & nano technology, and robotics. I think this bull market is sustainable and being driven by the correct fundamentals.