Two issues here - the first is that relatively new discoveries like the bidirectional gut-brain axis, and the major effects it has on you, pose a technical issu

Two issues here - the first is that relatively new discoveries like the bidirectional gut-brain axis, and the major effects it has on you, pose a technical issue to traditional thought experiments like brains in a vat (or robot as it may be). The second is that this also doesn't really answer the question. Your brain, like everything else in your body, degrades over time. It's not like it becomes immortal if you just stick it in a robot, if that were even possible.