I'm running Slackware which was first released in 1993
A new version comes maybe every year and a half.

Most any OS gets regular fixes, Microsoft's mistake was to add new features and change things in a fix pack. One of the Windows 2003 service packs came with a new feature called TCPChimney which caused all kinds of network issues which of course didn't surface in dev or UAT/performance test environments and took us a while to find and then disable across the rest of the servers. I'm amazed at the amount of $ corporate America looses to crap like that.

As far as moving off of Windows, there was an initial learning curve but its no more than the learning curve moving to a new version of Windows or moving to a mac. Once you get past that Linux is no big deal. I've gained back so many hours per week/month not having to do update/reboot/fix Windows, update the AV and antispyware, etc. The total cost of ownership is way lower.

I can't remember the last time I rebooted. And I do keep up to date. I type slackpkg update and go back to the forum I was on and check back later to see if its done.