The bond market, meanwhile, has been selling off.
But Curtis said that bonds are still very important to a portfolio. Instead of changing their asset allocation, investors can adjust the type of bonds they have, like putting their money into shorter-term bonds that are not as risky as intermediate or long-term bonds, she told "Closing Bell."
"We don't know what's going to happen after the first of the year. So it's not to say that all bonds are going to crash after January 1," she said.
For those who may be nervous about the market highs, Peter Mallouk, president and chief investment officer of Creative Planning, noted that "an all-time high by itself is nothing to be scared about."
Mallouk, who is also a member of the CNBC Digital Financial Advisor Council, thinks investors should have enough bonds to meet their needs — and that is all, since returns are expected to be muted.
"Anything can happen in the stock market, a terrorism event, a war, a trade war. That's why an investor should have money in bonds, so that your short-term needs, your intermediate-term needs can be met from bonds," he told "Closing Bell."
Instead of looking at shifting from U.S. stocks into bonds, he suggests investors look at global stocks, which have been depressed for the last several years.
— CNBC's Laura Petti contributed to this report.