In his case, it took him 22 years to advance from the first transformation of the second mortal coil to the tenth transformation. That is the time it should take him to complete each transformation in the third mortal coil.
These 22 years were because he used pills to extend his mental energy and increase the time he could continue to cultivate. There was also the boost from the Mountain Karma divine ability and the high concentration of mana in the environment.
If he can't maintain the conditions that helped him achieve the entirety of the second mortal coil in 22 years, it will take him longer than that to complete a single transformation of the third mortal coil.
But if he can maintain these conditions and even improve on them, for example, by cultivating in an environment with better mana concentration, then he can shorten that time greatly.
