Neither of mine are 'old'- one is almost three, and the other is about 18 months. However, I can see the age difference between the two of them- the 18 month pig still runs laps for fun, while 'big sister' tends to stare at her as if she wants to know why she's being so crazy! The three year old one still runs and popcorns and is in good health, but she doesn't have that crazy mentality that the younger one does anymore!