The brains are being artificially deadened by the blockers in the solution, per the article. They are probably thinking about what happens if they took those out...
No reason for a brain to die. Supply it with what it needs, and it can stay alive...who know how long. If you can feed the auditory and retinal input, you'd have something that has no haptic reality, but can still think, see, hear. Neural cybernetic links are doable.
Death as we always define it is nonsense. If the brain is alive, death doesn't come. We let the brain die when the body dies because of traditions so laser-etched into our souls that the body is the person. You don't die when your heart stops. The heart is a pump. You die when your brain dies. Sobering to think that the newly-dead person you are seeing in front of you maintains consciousness for a minute or so, in the dark and quiet we all get to greet at the end.