The rally could go deep into December, firm strategist Mike Wilson said.
Some on Wall Street are bracing for a renewed jolt of volatility over the next six trading sessions.
Overall, clients bought stocks across seven of the S&P 500's 11 sectors.
A reset in earnings expectations could prompt investors to seek an inflection point.
For one thing, it would be painful for investors, with technology and so-called growth shares likely taking the brunt of the suffering.
There's a pervasive feeling that the market has yet to price in the full impact of rising interest rates.
A wide gap between rising consumer and producer prices is starting to significantly narrow.
Brace for turbulence: Historically speaking, September has not been a great month for financial markets.
Technology companies are particularly at risk because many of them are valued on projected profits.
Wall Street lore says October is the most dangerous month for the stock market.