Are you using a bleeding edge distro? I've been using the version of xmonad from apt-get in Ubuntu (usually the latest release) for ~3 years and it's never broken or required me to change my config.
I'm using Arch linux and I've only managed to break XMonad once (or maybe twice) when I removed some packages that my config relied on. Admittedly my config file is probably pretty boring.
For what it's worth my XMonad config broke at some point, so I'm running an executable from october 2013. I've tried fixing it, but too much is broken for it to be an easy fix right now.