Not counting PowerBooks because those are not MacBooks
Mid 2007 17" MBP (Original)
Later 2007 17" MBP (Original)
Early 2008 17" MBP (Original)
Early 2008 13" MBA (Original)
Late 2008 15" MBP (Unibody)
Mid 2009 15" MBP (Unibody)
Mid 2010 15" MBP (Unibody)
Mid 2010 11" MBA (Unibody)
Mid 2010 13" MBA (Unibody)
Early 2011 15" MBP (Unibody)
Mid 2012 15" MBP (Retina)
Mid 2013 11" MBA (Unibody)
So I guess that makes it 12 to far! Yes I have been upgrading every year, but this year I don't think I need to. Every year I've had a reason to upgrade like faster processor, move to quad core, intensely better GPU, Thunderbolt, USB 3.0; the 2013 model for doesn't really offer much except a slight increase in speed which isn't worth it. I don't gain any new functionality (no touchscreen or fingerprint reader); Thunderbolt 2 is great and all, but I don't plan on buyer anymore Thunderbolt devices for the time being. However my old 11" wasn't do so well anymore, so I upgrade that to the new 2013 model and it's great; way better battery life and the increase to 8GB of RAM is very useful. I also will be buying the new Mac Pro, so I need to budget for that!