What is the primary (and aside from aesthetics, the only) purpose of a pipe? To smoke great. So when the pipe smokes great, it is broken in. I have pipes that smoked pretty great from the first bowl. To be fair, most of my pipes reached that great point in less than 10 bowls. Further, if they're not smoking great by the 10th bowl, they're not likely to ever smoke great.
I wipe my bowls after smoking, water cleanse and wipe again. I could care less about cake. To me, this idea that a pipe needs some thickness of cake to smoke great is absurd. If that were true, any material that would allow a layer of cake to form would then be suitable for being a great smoking pipe.