The answer to 'when to replace garbage disposal' is that you should typically replace your garbage disposal every 8-12 years, or when it stops working properly. Over time, the blades and motor can wear down, causing the disposal to become less effective at grinding up food waste. Signs it's time to replace include loud noises, jams, and leaks.
Replacing the disposal is generally a straightforward project that most homeowners can do themselves, but it's a good idea to call a professional plumber if you're not comfortable with DIY plumbing work. They can ensure the new disposal is properly installed and functioning safely.