I think its worth addressing the scope possible of contract magic, specifically of duration. From the sound of things, a few of you are thinking similar to the binder, where the pact is just for a day. My thoughts were often turned to longer term contracts, or contracts that last until a deed has been accomplished.

As an example, one might make a contract with a pixie to have it guide you safely through the demense of an very unfriendly frostwind virago. The contract would be completed once you were safely through and paid the price. Alternatively, one might make a pact with an archon to gain the tongues ability, with the price being the founding and funding of an orphanage. So long as you keep funding said orphanage, you keep the tongues.