I don’t understand how you charge hourly rates for shooting to begin with. Suppose you book yourself for a two-hour shoot on July 10th. Now a large client contacts you for a large project for two days July 10th and 11th. You turn them down because you’re working for 2 hours on the first day?
At the very least you should charge a half-day or full-day rate. We typically do not offer even half-day rates. It’s not like we can book another shoot for the other half of the day.
Keep in mind that part of shooting involves planning, packing up your gear, driving, setting up, shooting, breaking down your gear and driving home. Do you include all of that in your hourly rate?
I suggest you re-examine your business plan including your rates. Of course this is all just my opinion.