Temporary Life uses double of additional spirit of support gem

When add support gem it will reduce spirit right away.
But it will not be able to used the skill if you not also have enough spirit unassign

For example if you have Spirt 100
When you put Clarity and Vitality it will reduce 30 spirit right away
And if you used other 70 spirit all the way with other skill, you will be unable to caset Temporary Life unless you have at least 30 spirit untouch

(If you add more support gems on the skill it will be even more reserve and need to have left unused)

Interpretation:

Temporal Rift normally has 0 cost to have active, and 0 cost to cast.

Supporting it with gems that increase the Spirit reservation (like Clarity and Vitality), increases both the reservation to have active and the casting cost. The result is needing to have unspent Spirit due to the cost to rewind time, even though the cost should already be satisfied by the reservation while Temporal Rift is leaving behind afterimages.



I think there have also been people complaining about not being able to reserve all their Spirit with the Infernalist's Demonform, which may be the same core issue.