What is the life of a postgres back end process?

Are postgres back end processes connection specific? In other words, can we
assume / trust that they will be terminated and cleaned up when we close a
connection and that they will not live on and be reused by other
connections?

What is a good way to test this is the case which would account for
differences in load?

--
Eliot Gable

"We do not inherit the Earth from our ancestors: we borrow it from our
children." ~David Brower

"I decided the words were too conservative for me. We're not borrowing from
our children, we're stealing from them--and it's not even considered to be
a crime." ~David Brower

"Esse oportet ut vivas, non vivere ut edas." (Thou shouldst eat to live;
not live to eat.) ~Marcus Tullius Cicero