How long does flux paste last?

I'm curious to know, how long does flux paste typically last? Is it a one-time use product, or can it be stored and reused over time? Are there any specific storage conditions that need to be met to ensure the paste remains effective? Additionally, are there any indicators that the flux paste has expired or is no longer suitable for use? Knowing the shelf life and proper storage of flux paste would help me make informed decisions regarding its purchase and usage.