The darkness spell description says, in part (emphasis mine):
If the point you choose is on an object you are holding or one that isn't worn or carried, the darkness emanates from the object and moves with it. Completely covering the source of the darkness with an opaque object, such as a bowl or a helm, blocks the darkness.
Do you need to be carrying the item only the moment you cast the spell, or for the whole duration of it? Would the spell end if you're no longer carrying it?