What is a green parrots average lifespan?

They can live to 100 if everything goes right. 50-75 years shouldn't be a problem if cared for properly. It's a life long commitment and then some.

A carefully tended African Grey can easily make 40 years, and sometimes far more -- around 70.

An African Grey, with the right care, can live 60+ years. Most parrots are very long-lived, with even budgies living to more than 15 years.
an African grey parrot can live for 100 years

A carefully tended African Grey can easily make 40 years, and sometimes far more -- around 70.

An African Grey, with the right care, can live 60+ years. Most parrots are very long-lived, with even budgies living to more than 15 years.
an African grey parrot can live for 100 years