Since there's no battery and no moving parts, there's nothing to wear out or replace. The microchip will last throughout your pet's lifetime. My cat never goes outside. Unaltered pets in particular will take any chance to roam. There's a possibility that your house could be damaged in heavy storm, flood, or other natural disaster, causing your cat to run away in fear.
Pets can even be stolen-particularly birds and exotic or purebred animals.
No matter how closely you watch your favorite animal friend, there's always a chance she could get out, and if she doesn't have any ID, it will be extremely hard to find her. If someone else ever tries to claim my pet, the microchip ID number won't hold up in court. However, a microchip ID number is unique, it can't be changed, and it links a pet to its owner through an international database. It works a lot like the serial numbers that link vehicles, stereos, TV sets, and other valuable possessions to their owners. The American and Canadian Kennel Clubs have recognized microchipping as definitive proof of a dog's identity and ownership, and accept microchip identification to register purebred dogs.