Remember:
Spirits are not evil, but rather quicksilver otherworldly entities of inconstant nature. Some are channeled into the physical world through natural things, while others are messengers of higher realms, but all are volatile, hard to appease, and easily angered.
-Digital Grimoire, on Rasta tradition.
Lesson: Don't abuse spirits. They can abuse you back.
You misunderstood me; I don't abuse my spirits. In fact I ask them, thank them, and everything, I also talk with them sometimes and I don't have them do petty things like "bring me coffee" or something like that.
And that, right there, is where I like to break out Rule Zero just a little, in conjunction with the suggestion that the GM treat the Spirits like individual NPCs:
I'll generally keep track of how
everyone, not just the Magician, treats the spirits. The exact degree depends on the Tradition, but those results will adjust how much the Spirit actually works towards the best interests of the group and its members. I imagine Christian Theurge spirits will be more innately inclined to be 'helpful' than Black Magic demons, for example.
If the Street Sam has been treating the Guardian Spirit using Conceal on him well, for example, he might get a heads up about a threat he missed, or even a 'complementary' Counterspell assist if the group Mage isn't in position to do it. If Sammie-boy has been a douche, though, he might even get some inconveniently dangerous half-truths if not compelled to be honest via a Service, while the Magician, who treats the spirit great, will still get five-star performance when tasking the spirit directly.
Think of it like a Loyalty rating, for your Spirits... or maybe Faction Rep would be a better analogy, since it can go negative.