The duration of the 4th wave and the 2nd wave is not necessarily close. If the duration of the 2nd wave is relatively short, the duration of the 4th wave will usually be longer.

For example, the duration of the second major wave in the last bull market (2020.8.17-2020.9.8) was very short, lasting only 3 weeks, while the duration of the fourth major wave (2021.4.14-2021.6.22) lasted over 9 weeks, more than three times that of the second major wave.