Make fun if you want, but please unplug if you want to be safe. Two years ago I was rebuilding my father-in-laws XP system. The installation disk came with SP1, but SP2 wasn’t in place. I thought I’d go ahead and download SP2 before I got the virus software in place. It took all of 45 minutes for a worm to infect the beast. I had to wipe the drive and reinstall.
Take a look at your router history some time. There are probes from the wild internet CONSTANTLY. I run a web site and I have to monitor the logs. I only allow SSL input authenticated by WEBAUTH/Kerberos. (I also beat on my user base about the strength of their passwords.) Most probes are somewhat benign, but many are looking for specific weaknesses. Why take a chance when unplugging is so easy?
Yea, I guess you never know these days. Sorry for the snarkiness. Of course, it doesn't hurt to have a router with a firewall between you and the internet.