Haha, nice!
I completely lost track at Voya Nui as well (in fact, it takes a jog to my memory to recall that Voya Nui isn't the newest thingie...er, right?) and now I'm just a babbling...babbler.
I like to pretend that it stopped at Metru Nui, and after they all went to Metru-Nui, they came back, and just lived out Motago stories at Mata-Nui.