I've had Windows XP for almost ten years now, and I don't have to "manage" anything. Every year or so I wipe the drive with a fresh XP-CD install, and need to reinstall my favorite programs, but that would be true of any OS, whether it's Mac, Lubuntu, or Chrome.
Seriously? Do you really need to?
I've got a Windows 2000 install that's still going strong at 10 years old, and a couple of XP installs well over 5 years old. We even have a couple of Linux systems that have been running continuously longer than you keep Windows XP around - we only had to restart them during a UPS replacement. The Mac OSes only get upgrades (which counts as an install, I guess) when The Steve unveils a new version, so the system OS install I'm using right now is however old 10.6 is (about a year and a half). I have an install of OS X 10.5 on a PPC Mac at home that is still working just fine after 5 years.
So, this begs the question, what are you doing to screw up your XP installs in a year?
Even my boss, the resident malware catcher (seriously, I think he actively tries to get malware on his system) is using a three year old install of XP.
I think you'd be safe to extend your reinstall interval.