You obviously have a faulty phone
I have a Samsung Galaxy S and I need to recharge the phone approximately once every two days. It use to be more often but Froyo is much easier on power. I have had to reboot my phone 2 or 3 times since I purchased it over 6 months ago. I recommend that you turn off what you don't use and delete those programs that you don't want or will never use. If you still only have 8 hour battery life, I suggest you buy a new battery.
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