Not sure about the whole winter but I too, following on from Expressflight's comment, see 47 flights p/w in March 2016 compared to 52 last winter (although SXF ends 22FEB).
By June 2016 I notice there's no days with 3x AMS, is that a reduction or was that the case this year?
Also, judging by a current gap in the schedule for a Monday in June, I'm going to hazard a guess at CDG or IOM as the possible SXF replacement. Either one could fit beautifully between the MAH and VCE flights.