Given that, as far as I can understand, the most common interpretation of the spell is that it gives you X charges, and then you are "holding the charge" until you use all the charges to make successful melee touch attacks (plus the first attack after casting the spell) or you cast another spell.
Now, I'm having a few doubts about this spell when you cast it quickened:
Can you make a full attack in the same round?
Do they have to be normal unarmed attacks to make a full attack, or can they all be melee touch attacks?
Do you also make the touch attack given by the spell as soon as you cast it (from what I read, you make the touch attack as part of the spell even when you quicken it)?