The process is only finished, and the Immortal finally withdraws from the world of mortals, when the advancement progresses beyond the ninth refinement.
page 132
Ninth Time Refined
Elixir of Immortality: Nine Times Nine Selves
This final step effectively places the Enlightened Immortal among the ranks of the deities, ready to permanently discorporate (see Zenjoriki).
Page 161
This is the first step in the character's road to the Taoist version of immortality.
That is, at any time the character may choose to Discorporate permanently.
132 "ready to" v 161 "at any time".
I'm not sure if 132 is saying you are only then ABLE (at 9th refinement) to permanently discorporate (ie you could not permanently discorporate if you were only 8 times refined) or if "ready" is more like "willing to" because you're not supposed to discorporate permanently until you do all 9 refinements.
Similarly the context of 161's "at any time". Is this in the context of "at any time once you have this Zenoriki power" or based on the preceding sentence, is it in the context of "the Taoist version of immortality" which is at the end of "the character's road"?
Discorporate is a "step in the .. road" implying there are additional steps to get to "the Taoist version".
Is true Taoist immortality the actual act of permanent discorporate, or rather, does it refer to the freedom to do so, or being in the proper state of mine (9th refined) to do so?
The "dangerous trap" referred to under Restrictions on page 161 (60% chance of failing a save vs. temptation if you do it a 2nd time in 24 hours) seems to imply that you can permanently disporate as soon as you get the power...
But is this really the same thing, failing a save vs temptation, as making the choice to ascend?
The outcome of the failed save is "the character has departed and is lost" so maybe you haven't gone to the end of the road or back to the beginning, but fallen off of it? Someone who has not mastered the 9th step of refinement (ubiquity, being able to mentally inhabit other bodies you make, right after learning to transfer your mind into a Ichild) may lack the mental stability to actually hold their minds together in whatever new afterlife they progress to?