NIH also takes into account what is the proper amount to spend on equipment. Similiarly, if a large piece of equipment is being used to carry a light load, the time required to do the job will also increase compared to a smaller, lighter piece of equipment. Again, buying a smaller bike or trailer will only be worthwhile if the added depreciation and maintenance costs of the equipment doesn't exceed the extra NIH that will be earned making the run in less time. The runs are typically short, but need to be done promptly. Scheduled or time-insensitive runs, on the other hand, often do not need to be done quickly, but often take some time to complete.
Problems occur when a cyclist tries to do both types of work.
If a customer calls during that time wanting something delivered NOW, the cyclist will have to either have to turn the customer away or make the run late. Either way, the customer will be dissatisfied. However, I see nothing wrong with a cyclist doing a variety of work within one of these two categories. Nor does a cyclist need to specialize to do good work. Our customers have liked the fact that we do a variety of work.