I could speed up my 2nd excalibur, dualcast or a bracer I suppose. But what if I draw Zidane?!
Keep 100% reserve, use rest to speed up. Or is there some rush to use few moogles?
Some context is needed to answer these questions.
The safest answer is what Rixa wrote. You could always hold onto 100% of TM credit just in case you do pull Zidane.
But, to make an informed decision, you have to ask some questions:
-- What happens if Zidane is never drawn? All those trust moogles are wasted just sitting there in inventory.
-- Can Tariniel clear all existing content? If not, would re-directing the trust moogles to another TM that could be obtained now allow him/her to clear content that is currently out of reach?
Keeping in mind that there will always be more trust moogles in the future, so it's not like redirecting the trust moogles would be a permanent loss of Zidane's TM.
So, the question is, would Tarinel be okay with redirecting the moogles elsewhere and be willing to accept that if Zidane is drawn someday that he/she is okay with not maxing Zidane's trust the moment he is drawn. That's a personal decision to make.
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/start tutormode
As a pure logical aside to this, from the perspective of being my campus's business tutor, the concept of TVM (time value of money) states that anything obtained in the future is worth less that that same thing obtained today. This is because a person can employ whatever they obtained today to use to generate greater benefits than they would be able to while waiting for the future outcome to occur.
What this means in terms of TMs is fairly objective; buy now not later. Loosening the grip of cold logic a bit, the more realistic interpretation is that Tarinel could wait for a Zidane to appear in a draw. However, the longer Zidane takes to appear, the worse the waiting game becomes in terms of overall outcomes of the decision to wait, especially if another TM (like Power of Creation) would be the difference in clearing a future event or not. The deciding factor would be Tarinel's tolerance for waiting for Zidane to appear in draw. How much of a wait is too much of a wait? That's up to him/her to decide for themselves based upon their personal risk tolerances.
/end tutormode