Regular with Mirena?

Is it odd that I still have regular periods with the mirena after 2 1/2 years? My periods have shortened. Over the coarse if this time my cycle have shortened I think 4 or 5 days. Going from a consistent every 28 days to now I think it's 23? 24? They are lighter not heavy what so ever and it doesn't last as long either now. Sometimes before it would last 7 days and now at the shortest it's been 2 days but normally like 3 or 4. The reason I mention this is because everyone I talk to says their periods become irregular or vanish completely and my doctor even said this will happen.. but I've never missed a period. It's always right on time like always. Also, when I get it taken out will this be a benefit to becoming pregnant faster because I'm already normal?