The Pathfinder SRD says about Familiar Abilities:
Deliver Touch Spells (Su): If the master is 3rd level or higher, a familiar can deliver touch spells for him. If the master and the familiar are in contact at the time the master casts a touch spell, he can designate his familiar as the “toucher.” The familiar can then deliver the touch spell just as the master would. As usual, if the master casts another spell before the touch is delivered, the touch spell dissipates.
How long does a spell cast this way last? Is it like a stored bullet, since it says the spell dissipates if I cast another one? E.g., could I cast a touch spell for my familiar before combat, then during combat have it cast the spell, then I myself cast another spell?