It will carry on until the buffer is full, then it will slow down to write data to the card. The other thing to bear in mind is that it depends greatly on your shutter speed and AF settings. If you're shooting at 1/30s then you won't get anythng near the full speed, set it to manual 1/1000s and you'll see a big difference. If AF is in AI Focus mode the camera won't take a shot until it's got a focus lock which can also slow things down.