The rosy expectations reflected in the postelection bank sector rally may need to be tempered, said Chris Whalen, head of research at the Kroll Bond Rating Agency.
"Regulation is clearly headed in the right direction after years of punitive punishment from Washington and sure margins are going to expand. It's just going to take time," Whalen said on CNBC's "Halftime Report" on Tuesday.
Donald Trump's surprising victory is seen as a positive for the banks, as the president-elect has pledged to reduce regulation.
"Just having a Republican in the White House and ending the Spanish Inquisition of the [Consumer Financial Protection Bureau] is going to be a big, big lift for the mortgage market," Whalen said.
Traders also expect higher levels of inflation and U.S. government debt under the Trump administration, a favorable environment for the Federal Reserve to raise its benchmark federal funds rate.
But Whalen said that the fundamentals will take longer to play out, given that the "average life of a big bank balance sheet is somewhere between four and five years."
The CFPB did not immediately respond to a request for comment.
— CNBC's Vincent Caruso contributed to this report.