It differs from every person. I was playing with mine, eating, and drinking within hours of getting it. Just keep it clean, take tylenol or IBU (ibeprofun *SP*) to keep the pain down. As mykee said you will catch it on your teeth, I wouldn't take out the starter one until atleast 3 months just to make sure it won't hurt you when you take it out (or when you feel ready just give it a tug, if it hurts leave it alone, if it don't you can go ahead and try changing it.) You could also go to your piercer and they can usually change it for you, and usually at no charge.
Neptune, Zion, Enigma,