I haven't read Destiny yet either, but hasn't it been stated in GTTS that the torpedo most likely will only work once (or at least only temporary) because the Borg will adapt to it rather quick?
No, not just once. In fact, the reason transphasics are so effective is because they're just about the only weapon the Borg can't adapt to after only one or two uses. By their very nature, with the phase variations shifting randomly in each attack, they're difficult for the Borg to predict well enough to adapt to. So they probably have a longer "shelf life" than any other anti-Borg weapon. But as Allyn says, they're like antibiotics: eventually, the enemy will adapt, and the more heavily you use them, the sooner that happens.