On a standard non-jailbroken iphone 3GS you can create up to 11 app screens by default. And if you have created more than that without jailbreaking (without using anything like Redsnow, Quickpwn,) then you can boldly march towards your apple store to get their comments, I congratulate you on your achievement. But if you have used any of the above tools then your warranty becomes invalid and will not get any support or replacement in case of damage.
So make sure what you've done doesn't make the warranty invalid.