i had that problem in the beginning when i first started coming to this board.
it turned out that some of the emails ended up in my spam folder and since i never saw them or went back to the thread i didn't get any more emails.
but now none of the emails go into my spam so i don't have that problem any more.
i do visit the forum every day though, even if its just for 5-10 minutes to see whats going on.