A betta normally lives to about 2 years old, sometimes you will have
     a betta grow as old as 3 to 7 years, older than 3 years is rather rare, 
     but there has been at least one documented case of a Betta splendens 
     living to be 9 years old.  Most bettas under good conditions live to at 
     least 2 years of age.  If your betta has suffered from illnesses or 
     other bad conditions it might live a great deal less.