This sport at some point has to move on from these legends. I hate to say someone shouldn't make a living at what they love to do but there is a reason why an org has never been created around these aging fighters or even some type of legends division within an existing org. Fans may tune in for one off fight for well past his prime fighter against another past his prime fighter but they won't tune in over and over for those fighters. Not to mention, even though they're past their prime they still demand big money.
Silva should just beg the UFC for his one last fight in Brazil against someone like Wandy, Vitor, or Chael again and call it a day once and for all. It does zero good for Anderson to fight any relevant fighter.