I did find one where you could make someone a werewolf longer by 2 sim hours, so instead of transforming to a werewolf at 8 pm and going back to normal at 6 am, (time length: 10 hours) you can transform to one at 7 pm and back to normal at 7 am. (12 hours) The link is posted below this message. Now as far as transforming to and from a werewolf at will is concerned, I haven't seen any mods involving that. Then again, if a werewolf could transform at will, they'd be an animagus. I think any werewolf purist (such as myself) would agree to that, due to the fact that if you were a werewolf, you'd have no choice but to transform unless you get cured. Besides, where's the fun in not making your Sims slaves of the night?

Hope this clears up some things,
BillieJean (insert two bunnies here)
MTS link: (Mod made by poifectly_poiple)
http://www.modthesims.info/download.php?t=284247