Does It Really Take 30 Days to Break a Bad Habit?

I have no clue if it's possible to break a bad habit in 30 days, but I'd like to experiment because I bite my nails ALL the time. I have tried to break this habit through a trigger (snapping an elastic band on my wrist) and bribery (my mom said if I didn't bite my nails for one week she would give me $100). Neither of these worked. So I've checked around the internet, and I'm going to try to break my habit in 30 days, but first, there are some steps I need to take:

1. Admit that I have a problem: "I, F. Dunner, solemnly swear that I have a bad habit of biting my nails.
2. Change your environment. Since I bite my nails when I sit on the orange couch and watch TV in the family room, I am going to switch to sitting on the blue beanbag (I could give up watching TV but if I'm being realistic, that's not gonna happen).
3. Create barriers to that habit. I am going to give my family permission to charge me 25¢ each time they catch me biting my nails ("catch" being the operative word here––no hearsay). 
4. Find something to replace that bad habit. I am going to knit when I watch TV so that my hands will be full. At the very least, I'll get a sweater out of this.
5. Be patient––this could take longer than 30 days and more than one try. 

Wish me luck, everyone!