These tips will help you get the best battery life:
1) Use good quality Alkaline batteries. Some cheap batteries are only suitable for low-drain items such as remote controls or clocks. Good quality Alkaline batteries should last much longer.
2) You can use re-chargeable batteries. NiMH rechargeable batteries can last even longer than Alkaline and only cost pennies per charge.
3) Mount the Rockit as close to vertical as possible (pointing up with the button on top). Battery life will be reduced if used horizontally (lying flat).
4) Try different speeds, using the dial on the bottom. Sometimes the best rock can be achieved at a slower speed (for the technically minded - this is called the resonance frequency)
5) If it fails to start when you press the button - try nudging the speed up a little using the dial on the bottom. That is often all that is required rather than new batteries.