To put those numbers into some context, here are the subsequent 12-month returns for all months going back nearly 100 years for the S&P 500 (~100 years * 12 months/year = roughly 1,200 data points).
The S&P 500 has delivered gains of 15% or more for three consecutive years only eight times since 1926. There's no clear historical pattern regarding what happens in the fourth year after a hot streak ...