A world where, instead of aging in years, the people age in knowledge. So, instead of dying once a general age was reached, they die once they achieve a certain amount of knowledge. A man could live forever if he never learned anything, or could die after reading a few choice books. Of course, the knowledge of the land would be regulated, like medical drugs.
There is a race of beings that have endless lifespans. Because of their eternal existence, the only forms of time which they understand are being and non-being. They do not understand words or ideas such as past, future, present, yesterday, today, tommorow, then, now, when, until, ect. They do understand yes, no, live, die, on, off, there, not there, existent, non-existent, ect.