Someone else may be able to answer this a little better than me.
No one really knows how blizz works. They have the ability to detect how long you have been signed onto their network, I'm sure. I would be very surprised if they didn't. However, playing 12 hours on one toon and 12 hours on another can have its benefits. A lot of people claim that the bans come from player reports. If that is true, then splitting up time will make you less obvious to other players. If someone logs on in the morning and sees xxxxxx (Your botting toon) killing mobs in a certain area, then goes to work and comes back 12 hours later and sees xxxxxx still in the same area, then they will be very suspicious. Now if they come home from work and see yyyyyy (Your other botting toon) they won't know it was you. Playing 12 hours a day means you are just a regular wow addict (no offense), playing 24 hours usually means someone is botting. Of course some people have played for 24 hours.
Some people also say that blizz looks the other the way when it comes to botting. If blizzard were to ban every botter they would probably lose more money then if they just looked away. Really its kind of convincing. Some botters have over 50 accounts. They make over 100$ for the actual game, per account, then 15$ every month, per account. Also they make money by transferring the toons around. Blizz then may ban those accounts after a few months which then the botter will usually go buy more accounts again. Its kind of a win for blizz.
