Has your linux system ever been compromised ?
 

I dont do updates, upgrade kernels etc.
I use a distro for a couple of years, then install a new one.

Has you system ever been compromised because you did not do proper updates ?

How unsafe am I ?

Perhaps you should run your system as a LiveCD. You would pretty much be garaunteed to be free of problems. No programs could be over written.

I used to use an old pc with two nic cards and configured as a router to attach my home lan to the internet. It had no firewall. It was compromised and made unusable within about a month. My current 'router' is a Slackware 10.1 machine, also with two nic cards. There have been MANY break in attempts, which have so far been unsuccessful. I'm in the process of increasing the security of my firewall. Break in attempts are ubiquitous. Five minutes after I rebooted my machine, I had an attempt from China. It doesn't take to much effort to securing the machine. You might find it worth your time.

Not that I know about ;)