I worked as a contract employee for 15 years. I also worked for 5 years split between two "real" jobs. Now I'm self employed, which is different from contract work.
Let me tell you something about contract employment. First you never really have a vacation unless you get a contract job that is longer than 1 year. If you are in between jobs you have the stress of not having an income with no prospects of ever working again. When you are working people don't want you to take time off because they have a requirement for a temp to show up every day for a certain period of time. So vacations don't really exist.
Next is the ANNUAL income. It might seem like making 50% more money while you are employed is great but you may be unemployed for months between jobs. There have been good years and bad years financially for me but I had two periods of about 8 months between jobs. That can get on your nerves. If you are married it may become a problem for your spouse.
Your contract house may or may not offer health insurance. If it does it won't be cheap. If it doesn't you're SOL. My home state, Massachusetts, is just now deploying a program to make individual health insurance possible. Until this point I had gone without health insurance when I was contracting. Frankly, that puts everything that you own at risk if you have a dramatic hospital experience. I was lucky. The only time that I've had an expensive hospital stay was several years ago at my second "real" job. That hospital bill was $15,000 of which I had to pay $3,000 while my health insurance paid the balance. If this had happened when I was on a contract job I would have had to pay the whole cost. That would certainly have taken a nasty chunk out of my life savings.
The people that you work with, the "real" employees of your clients, will envy your hourly rate in comparison to theirs. They may be very hostile to you.
Don't EVER complain about the behavior of your client's direct employees. You are always an outsider. The direct employees are like the children of the management. If you complain about one of the client's direct employees the result will be exactly as if you had complained about a child to its mother. You will lose.
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Now let me tell you why I stayed with it. It is all about the kind of personality that you have. I happen to be one of the people who, when they have a "real" job, feels trapped in a situation where I am working with people who don't share my commitment to excellence and with management that are idiots. Briefly, I am one of those people who is a chronic malcontent. I find that I can put those issues out of my mind when I am working as an independent service provider rather than a direct employee. When I am a direct employee I feel that I have a responsibility to the business' shareholders and their customers to do everything possible to correct problems. In contrast, when I am an independent service provider I can just focus on doing my part of the job as well as I can while not looking at the structural problems in the business.
I would say that if you can be happy working as a direct employee for a business then you should probably do that. I would further say that anyone should only get into contract work or self employment if they are miserable working in a direct employment position. Direct employment is much easier. The difference in pay is not the reason to start contract work. You could end up making very little in any given year.
I hope this helps.