It's been an easy few years to make money.

Barring a late Friday plunge, the second quarter of 2017 will go out as the S&P 500's 16th winning quarter out of the past 18. The large-cap index has risen by 2.7 percent in the three-month period.

Throughout the whole history of the S&P 500, which dates back to 1928 if the performance of the earlier S&P 90 is incorporated, there have only been six prior four-and-a-half-year periods in which the S&P 500 rose in 16 quarters or more. All of them came in the periods that ended between the fourth quarter of 1998 and the first quarter of 2000, according to a CNBC analysis of FactSet data.

That is to say, the S&P 500 hasn't performed this dependably since the dotcom bubble.

Yet while today's quarterly streak is the same as yesteryear's, the qualitative performance is very different. The S&P 500 has risen by about 70 percent since the end of 2012. Contrast that with the S&P 500's 156 percent rise over the same amount of time the last time such a win streak was seen, in the four years ended in the first quarter of 2000. Or the startling 199 percent gain in the same amount of time concluding at the end of the second quarter of 1999.

Still, looking forward, strategist Max Wolff of 55 Institutional says the streak is about to be broken.

"The S&P is and has been overbought for a long while. It should slump," Wolff wrote in a Thursday email to CNBC's "Trading Nation." "We expect the summer or early fall to mark the end of the run."