it depends. if your tama has a baby it will age 2 more times and then die. if it doesn't have have a baby, it turns into an older charecter. and i have no clue how old it lives to be. im sorry, its never happend to me efor. im guessing mabey around 11?
I don't think there is any set age that Tamas die.
My Memetchi turned into a Ojitchi (old Man) when he was 11yrs old - he's 16yrs old now - but they can live a lot longer - I know of some that lived to 45yrs and 60yrs!