A fresh set of alkaline batteries should last, depending on amount and type of use, up to 30 hours. This can vary greatly based on certain factors, such as Wii Remote Speaker Volume, Rumble, battery quality and age, and type of game being played.
If you are using rechargeable batteries, the only type of battery recommended are Nickel Metal Hydride batteries. When it comes to using rechargeable batteries, you must follow manufacturer guidelines for safety and proper usage. Failure to do so could cause damage to the Wii Remote and void the warranty.
The Wii Remote will go into sleep mode if the console is turned off, if the console goes into Burn-In Reduction mode, or after 5 minutes of inactivity. This will conserve battery power.
If you still feel that the Wii Remote is draining batteries too fast, then it will need to be repaired. Please contact Nintendo Consumer Service for more information.