Subject: Is there any living being which does not die of 'natural death' ?

I understand any animal would eventually die, even if placed in "ideal" living 
conditions. But as some plants are thousands of years old, I was wondering if, 
placed in theorethically ideal conditions, plants would finally die ? In other 
words, and more generally, is there any living being which does not die 
of "natural death" (but only of external accidents).

Re: Is there any living being which does not die of 'natural death' ?