I've completed my first Tamagotchi P1 life cycle today.  He died of old age at 7 years old.

Babytchi ---> Marutchi ---> Tamatchi ---> Nyorotchi

Yes, my adult was the second unhealthiest P1 character you can get.  It was due to that one incident in his tamatchi life where I actually missed taking care of him alongside my other 10 active tamagotchis.  He beeped to call my attention, and I saw that all his hungry hearts were empty while his happy heart was at one.

Nyorotchi as Tamagotchi Mobile pointed out, was very sickly.  He needed attention quite often. 

I'm just glad that Bandai chose to have generations in their future tamagotchis.  I'm sure back then, kids were crying because of their pet dying of old age and becoming an angel.  It's a bit easy to get attached to these little critters.