Why do Maya's preferences get reset when it's reopened?

Had a nasty case of certain Mya preference (specifically Maya's autosave) states being reset when Maya was reopened.
Come to find out, a function my userSetup.py was calling to, was executing this line of code:

import maya.cmds as mc
mc.savePrefs(general=True)

It appears that trying to save prefs while Maya is opening is a very bad idea.