All depends how often your members get near a player running the YG Updater.

Best way is to get members running the YG updater (http://forums.yg.com/showthread.php?t=593) - and it's even easier with the AoC QS util (http://aoc.curseforge.com/addons/aoc-quick-start/)

Without the YG updater picking up people YG won't update - !yg itself can't do this.  I know there used to be some chars at certain places on servers that would update but not sure nowadays - I've always run the updater myself via AoC QS.