1/ A perfect market timer who bought the market at its lowest PE in...

Even if you are timing the market to perfection, it's the business' performance that matters the most over long periods.
If you are a long term investor, you are better off getting a grasp of the LT opportunity than focusing on what the right multiple is (extremes aside).
Valuation should never be disregarded, but it should be given the necessary context. What matters most depending on your investment horizon? Find out and focus on that.
