Periods with MIRENA (specifically this type of IUD)

I've read all sorts of possibilities online as to what my period could be like, but few real (personal) experiences. I've had my Mirena since June (so for 4 cycles), and so far all I've noticed is slightly shorter periods and a different type of cramping. Did anyone have their period truly diminish and/or reduce to spotting? When would you say that it occurred? Thanks for your input!