I do the same thing and take my pills for a few months at a time skipping the placebos. I'm not sure what you're referring to when you skip the reduced hormone pills, because I thought you could only skip the placebo pills if you were on a monophasic drug (not triphasic).
To answer your question, though, I also get break through bleeding if I've been doing this for 3 months or so. I think it just means that your body is ready to have a period. If I stop taking the pill then, I'll usually get my period 3-4 days later and then I can start all over again. The breakthrough bleeding almost always happens for me when I've been taking the pill non-stop for a long time.
I take Yasmin or Ocella (the generic form of Yasmin). What pill are you on?