Werewolves--how long should it take?

I have a sim who's been maintaining a 100/100 relationship with a wolf
(glowing eyes, etc) for weeks now, yet the SOB won't turn into a werewolf.
Am *I* supposed to get this 'nibble' option somehow, or is the wolf supposed
to decide (randomly) on his own to do it? Is there anything that can
further influence a wolf to bite my sim? The worse part is that this house
gets this wolf visitor daily--yet nothing happens...

PS - no cheats/hacks here