Will Fernet’s key function at any timeframe? I’m very new to cryptography and I need to use a symmetric cryptography approach.
My simple question is, will the key always at any time be able to decrypt the encrypted text?
The encrypted text may be years old, and key will be saved years before as well.
Is there any time factor applied that may make the decryption fail?
No, there is generally no time factor when it comes to decryption.
However, you should remember that even a single changed bit can cause decryption to fail. This is especially the case if that bit is part of the IV, authentication tag or nonce. So I'd rather worry about storage of keys and data. Disks may get stuck, flash may degrade or loose voltage differential.