OT: Should computers stay on constantly?

[Slynky]

Suicide Junkie said:
A NAT is not really a firewall.

And lacking NAT dosen't make it a better router.

NAT isn't a firewall but, without looking back at reference material (in other words, in laymen terms...), it's my understanding NAT logs a request for info leaving the router and when a data packet comes in response to that request, it is allowed to penetrate the router. Any packet coming into the router for which there is not an outstanding request is turned away.

This is the way I understand NAT (but I could be wrong).

So, in theory, this seems like good protection. But, as in anything, multiple barriers are the desired defense, so NAT is just one component of mine.