How long...

From my submission to /.:

I'm sure everyone knows the story about the life expectancy of an fresh, unupdated PC once it's connected to the internet, but what about a PC which just hasn't been updated in a while? I've been deployed to Iraq for the last 9 months, and haven't been able to hook up my laptop to the internet to get updates (I do HAVE access, just can't hook up a personal laptop, gov't only). Before I deployed, I would update my software (system, anti-virus, firewall, anti-spyware, etc) regularly, but as I get closer to coming back to the states and my broadband connection, I'm beginning to wonder what the life expectancy of my PC will be. What's the lifecycle of a security exploit, hack, virus, etc - between discovery/release, propagation, and extinction (or a state approaching extinction)?