My basic rule for not losing money, which I hate to do, is never invest when the market is not acting normally, like now.
In the end, price action is the only indicator that really works. And this price action just keeps going up and up.
At some point, reality bites, but my gut says we go up into end of this week, and more likely into end of next week.
BTW, shorting on aug 31 works a lot of the time, and the big top in 1987 was on August 25th.