Tash will wear off after a few minutes.
And if you have to do stuff like that when charm-grinding, it'll barely be worth it. Just doing it the traditional bluebie way is tricky enough and it doesn't take very much to fuck it all up. If you have to juggle back and forth with charm, charmbreak, tash, charm (not to mention keeping numerous junk buffs up) just to protect the pet a little from getting dispelled, the whole charm-grinding idea is shot and you might as well use your summoned pet.
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