How Long Does Plumber's Putty Last? 

Installed plumber's putty can last for years if undisturbed. However, unused putty will quickly dry out if the container isn't airtight. 

Putty is primarily used to seal sink drains. Once installed, it stays flexible and effective for years. It is not an adhesive and doesn't harden, making future fixture removal easy.

Throw away unused putty if it feels dry or crumbly. Installed putty only needs replacing if the seal leaks, the putty cracks, or if you remove the fixture.

No. It stays soft and creates a watertight seal via compression. 

Replace it if the seal leaks, the putty cracks, or when a fixture is removed.