I got the mirena in June of 2013. So it's been well over two years and now my periods are lasting so much longer. They used to be only a few days, but then they started getting longer. The cycle I'm currently in has lasted for 2 weeks and 2 days and is still going. It will stop for a little less than 24 hours and return again. It's not like a heavy period or even a regular period. It's just a continuous discharge ranging from reddish brown to bright red along with light to extreme cramps.
I haven't had my mirena checked since I had it put in, I don't have any insurance.