So how long have you gone without paying your Rundfunkbeitrag?

You all know it, the incessant, merciless stream of letters sent to your house reminding you that you owe 20 euros a month to Big TV/Radio whether or not you even watch a single TV program or listen to a single radio station. Even those without a TV (such as I) still get harassed by them. The reasoning is as ridiculous as the amount.

I've have no problem in paying my taxes, medical insurance and any other legitimate Steuer, but this is definitely one I cannot abide. But I've heard many times that it's 1) inevitable and 2) inescapable. If you don't pay it for a long time they will eventually come knocking on your door. Is this true? If so how long until they do? And is there seriously not a single way around this asinine policy?