A couple of things:
First of all I agree that the US market might continue to rise and end up in bubble territory. Low interest rates, lower unemployment, lower oil prices etc lead to a steadily improving economy which will improve confidence and drive equity markets.
But I also think timing the market is foolish. When you say that you have a high allocation in cash and deliberately limit your investments I think you are doing just that. In my opinion it is ok to hold cash and sometimes lots of cash, but it shouldn't be a *decision* that is based on
1.) a ratio
2.) media coverage
3.) Hussman
4.) the length of the bull market
5.) anything macroeconomic
6.) sentiment
7.) technical analysis
8.) or in general your "view of the world and the markets"
It should be the *result* of your usual bottom-up investment activity: Depending on the available opportunities your cash allocation goes up or down.