i think you've answered you're own question there age. i think an important aspect is that agent smith was neo's nemesis, his opposite, the other half of him. implicit in that relationship is interdependence, agent smith is irrelevant without neo and vice versa. in summary one cannot be destroyed without destroying the other. the oracle tells neo this, so he knows it. the next bit you can take one of two approaches, either neo has a buddha style enlightened knowledge that his human form is temporary and gives it up, or, after trinity's death he no longer has a reason to stay alive and can die for his cause. now remember that smith escaped the rule of the machines when he jacked up into cypher in reloaded and the machines are searching for him. neo has jacked into smiths world via the machine (not via a ship from zion), so when neo becomes enlightened he allows smith to enter into him, destroying himself, but delivering smith straight to the machines, ensuring the destruction of smith. neo lives on, again i can see two ways of approaching this, either because of the belief that the zionists have in him ( it appears he will be the symbol of their new faith) or, if you're going with buddhism, because he never begins to exist so can never end. :-) and don't worry, i do intend to get out more often :-)