You agree with the adage "buy low and sell high" right? Well, don't forget to sell. US stocks are expensive and current valuations have rarely been higher.
When the market PE reaches 20, it's time to sell. That's where we are today. Have a look at the following chart from Acting Man blog:
Stock market valuations have only been higher about 2% of the time during last 90 years. The odds are in favor of the house. Be forewarned.