As a Personal Concierge/Lifestyle Manager, I have found that it's pretty customary for people to charge by the hour. It took a conversation with a coach to help me understand that terminology is everything. She told me not to use the word "Services" (a point I still struggle with) because, as she put it, "hookers perform services" and it made me think of another point - you know what else hookers do? They charge by the hour.
Don't get me wrong, I'm not saying that there is anything wrong with people who trade their hours for dollars. Employees do it every day, at Wal-Mart, Burger King, Sonic, etc. CEOs are salaried. You're the CEO of your business, right? When's the last time you heard of a CEO getting paid hourly? As an entrepreneur, you should be thinking in terms of salary, not hourly, especially when you're awesome because you're the CEO of your business.
So, I started doing a little research on the downside of charging hourly. The first thing I ran into was the quote from Taylor Lindstrom in a post by Jonathan Fields - "Death By Hourly Wage." Last night, I came across a post that said "Selling hours is a conflict of interest" and directed to a complimentary download of a nice, informative booklet that details why it's a conflict of interest.
The challenge is helping people who want to work with you think differently. Several people have asked me "what do you charge by the hour?" I plainly explain to them that I don't charge hourly because I'm great at what I do and what may take one person 2 hours to accomplish, I could possibly do in 20-30 minutes. You're paying me to save you time - not paying for the time it takes me to do it. Once people come to that realization, things tend to run a little smoother.
It's up to you. Run your business in the way that best suits you. The clients you are meant to serve will understand and as people grasp the VALUE of what you provide, they will be less focused on the hours it takes you to do it.