Quietly, the stock market just passed a major milestone, and is close to making a new one

Is this the untameable bull market?

In a year of records, stocks just made another one that speaks to the enduring strength of this bull market.

The just posted its second-longest streak ever without a 5 percent pullback, according to a new report from Deutsche Asset Management.

"What to make of the recent gains on Wall Street? One way to gauge the strength of the bull market is to ask how much the market has risen since the last correction. Another measure might be how much time has passed," the firm wrote in a Friday report called, "Visualizing the second-longest uninterrupted bull market in Wall Street history."

To reach its conclusion, the firm counted the number of calendar days between the Brexit referendum in late June 2016, when equities in the U.S. dropped by more than 5 percent, and Thursday's market close. After 487 calendar days without such a decline, the current stretch of trading sessions without a 5 percent pullback "ranks now as the second-longest such episode since 1970."

"There was only one period between December 1994 and May 1996 when the market managed to rise for longer, without dropping by 5 percent or more in between," according to the report.

Should the S&P 500 continue its climb higher without a decline of more than 5 percent until Dec. 13 of this year, the market's streak will mark the longest such episode, surpassing the winning streak notched in the mid-1990s.

Interestingly, however, the index is not on pace for its biggest increase in that time. The current streak, the report notes, ranks only 13th since 1970 in terms of index gains.

Some market strategists are more anxious about equities' valuations, by multiple measures, more so than the duration of time that has passed without a pullback.

"I am a little concerned because of valuations. They've been stretched for a while, but now we're getting not just [price-earnings ratio], but price-to-sales, market cap to GDP, all combined at levels that are usually followed by a period of underperformance or poor performance in the stock market for three to five years, or even longer," Matt Maley, equity strategist at Miller Tabak, said Friday on CNBC's "Trading Nation. "

As such, Maley said he would advise investors to consider "taking a few chips off the table" heading into the end of the year, and focus on the market's internal rotation.