I have seen irregular breakthrough bleeding and spotting not occuring at all, last through the first 3 month cycle, stop somewhere in the second 3 month cycle and even last for over a year and with some women, indefinitely. Different women will react differently to the hormones.
It is a bit of a bummer as you are taking it to stop the bleeding for 3 months at a time and now you have more irregular and unannounced bleeding than before.
I would say that if it lasts past the second pack
(6 months) that you should look at alternatives with your health care provider if it is a problem for you.
Best of luck!!