You will find that the larger the batches of items you process at a time, the less time it takes, per item, to produce them. This is known as economy of scale and just like in real-world manufacturing you can use it to your advantage. Since the game doesn't really allow for mass production models, what you will be doing is much closer to batch production. The larger the batch you can work on, such as prospecting ore, the more efficiently you will be using your time. For this reason alone you should be equipping your characters with the best bags you can afford, because the more bag space, the more a character can work on in one batch, and the more time you save since you have to make fewer mailbox or bank trips.
The biggest advantage in using big batches is that the tasks that can be more or less automated and don't require your attention can be done in the background while you can do something else like checking your e-mails: