Depends entirely on the encounter, if the encounter has a lot of downtime you're going to have enough TP anyways, if it got short downtimes were you can charge chakra you can use those to purify instead, only thing were this is really an issue is on the SSS dummies were if you have more than 700 SkS you're going to run out of TP before the dummy is dead so purification is needed anyways, in this case you can use fracture multiple times during the fight without running out of TP.
