How long do ETs live?
The people of Zar's race are the longest living of those that visit Earth at about 1000 years, counted in Earth years.
The people of most of our visiting races live hundreds of years. 
Most races in our area live hundreds of years.
The longest living people that visit Earth get to be about 1000 counted in earth years.
The race that lives to be about 1000, that visits Earth, is over 6 billion years evolved.
They are genetically refined and take very good care.
I think their metabolism is just right for them, and has no comparison to ours.