For investors interested in factor-based strategies, a recent Barron’s article suggests that it can “take longer than most investors are willing to wait for signs of success.”

The article cites comments from Gregg Fisher, founder of Gerstein Fisher (which managed $3 billion using a factor-based approach), who say investors should “shift their factor mixes as time goes on to reduce the likelihood of an ugly surprise shortly before retirement.”

According to Barron’s, Wall Street is “awash in statistician swagger. Some 1,300 exchange-traded funds use a factor or ‘smart-beta’ approach in an effort to boost returns, reduce risk, or both,” adding that at the end of January assets totaled close to $700 billion. The article offers an overview of factor-based investing’s chronology and highlights a working paper that uncovers what it describes as a “scandal in Factorville.” However, some of the longest-tested factors, it reports, “survived scrutiny. The takeaway for investors is to stick with the classics.”

The article also points out that some of the best-performing factors “aren’t necessarily the right ones for every investor, at every moment,” adding that diversification among factors is a wise approach. “For now,” it concludes, “investors can create their own mixes of factors using low-fee ETFs.”