With all the other summoning going on at the upper levels (armor and weapons for pets) and the relative price of reagents (Malachite, pearls, Cats Eye Agate), I'm not sure if the risk/reward for putting this on is worth it if you have a halfway decent necklace on, already. It hasn't happened (yet) but I'd feel REALLY stupid if I left this on while my good INT/RESIST necklace sat in my bag just becuase I was too tired/lazy/stupid to not switch back. Even worse, imagine putting one's permanent necklace in a no rent bag for some stupid reason and then go LD for more then 15 minutes. Just a thought, but reagents are pretty cheap by the time you get this item.
It is nice for your pet, though, so there is a definite use for it.