It is not the level of the market which you should concentrate on, it is its underlying fundamental's.
The market is simply a reflection of the overall economic situation, only in this case its value is artificially juiced by the fact that fixed income investments have been made a losing proposition.
The two factors that really need to be monitored are the interest rates and the chances of recession.
There is 0% chance of interest rates going down from here, and possibly a 50/50 chance of them increasing. The chances of recession are growing every day as debt loads increase and world trade decreases.
Margin in the market has never been higher, and that is a big danger sign. In addition, baby boomers who make up the largest demographic in the market have begun as of this year to be forced to make mandatory minimum withdrawals from their 401K's. With millennial's financially struggling with student loans and almost a 3rd still living at home, it is doubtful they will be in position to purchase the equities that the boomers will be selling.
None of us can predict the future, but we all can assess the present and use critical thinking to calculate the most reasonable conclusion about what the evidence is telling us....