So far I am on a 6 month cycle.
Been banned the last 3 waves using only rotations on my main; here is my system:
1 Account that has all my max level chars (main)
4 Accounts I use as feeders
I pick 1 or 2 toons I want to play, move them to one of the feeder accounts. When banwave hits, I go back to main and xfer another to another feeder. The way the rotations work i'll be getting back another account next week roughly 1 week after waves. Luckily, xmog/rare titles such as arena master and mounts are all tied to the battle.net account so when I move a char off the main to an "expendable" account I get to keep all my hard to earn back shit.
Eventually my rotation wont work as every time you get banned you get double the punishment so at WORST case I am buying another game copy which if you look hard enough can cost around $40. I am at the stage in my life where I can drop 40-60 without it even denting my financial situation. If I have to buy stuff every ban wave then it's not so bad.
What would fuck me is if ban waves become more frequent or they start banning battle.net accounts. I figure I can only muster another year at most into this game anyway; it's going to eventually be on life support as it can't go on forever. I bet after next expansion it will be curtains for wow.