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It's a nice idea, isn't it? You've got so much business already that it seems logical to just shift over to all freelance. Unfortunately, it's not always so simple.
First, when you say you're making more money freelancing than you earn from your full-time job, are you adding back in the social benefits paid for you? If your place of employment covers or collects for health insurance, a pension, taxes, etc., then you need to make sure you've added those sums back into your equation. In the US, this may add as much as 40% to your "true" compensation. Ditto if your employer pays for your vacation time or job-related education.
I've been working as a consultant to micro-businesses and independent business owners for about 15 years, and I've been teaching courses in the basics for at least 5. I see many many people who open their own shop because they have so much freelance work, only to find that the initial momentum dies in 18 or 24 months. I don't have the current statistics at hand but in the US some enormous percentage (it could be 70%) of all small businesses don't make it to the 4th year.
Which doesn't mean if you open a business of your own you won't be successful. But if you need what you earn in order to live then you owe it to yourself to plan, and to plan well.
Here's a link to a recent article on the topic. Phyllis Korkki, "Taking the Leap to Self-Employment New York Times Published: June 19, 2010
http://www.nytimes.com/2010/06/20/jo...rkki&st=Search