5 things to remember as Dow moves past 22,000 3 5

10,000 and 20,000 along the way.

The point: Stocks tend to rise over time and often can make a string of new highs before stocks make a final top.

The Dow has been on a tear and has more than tripled in value in the past eight years. So with prices no longer cheap, future gains might be less robust.

When stock prices relative to corporate earnings get super frothy, like they did in 2000 when the Nasdaq composite was trading at 107 times its earnings, it could be a signal that the bull is overheated and could cool off.

(On average, the broad market gauges tend to trade around 15 or 16 times earnings.)

Currently, the Dow has a P-E of around 20, according to S&P Dow Jones Indices.