I remember the Tamagotchi crazy back in the day (this is a very well done play on it, really enjoyed the linked site) but never owned one (and am not sure how t

I remember the Tamagotchi crazy back in the day (this is a very well done play on it, really enjoyed the linked site) but never owned one (and am not sure how they worked exactly on a technical level). I wonder if it is technically possible that some of them are still "alive"? I wonder if the programmers made any implicit assumptions about lifespan that were tested by now (assuming the batteries could be changed without "killing" them).