Sure, but maybe the assistant gets distracted by other work, or gets sick and don't get a chance to make sure someone else does it, or quits because their boss

Sure, but maybe the assistant gets distracted by other work, or gets sick and don't get a chance to make sure someone else does it, or quits because their boss is a jerk, or any number of other things going wrong. At least a few of these will happen over the course of two years.