dont believe i have ever done 50 in one year but I know i once did 12 queen size and as many crib size ones one year due to my prolific relatives. i hand quilt all my quilts. I made a queen size trip around the World quilt in two weeks once. I actually made more quilts in a year while working full time (or one ft and one 1/2 time job both at same time), raised 5 kids, and kept house then i do now that kids are grown and i've retired.
i see articles in quilt magazines where they will say that someone has made so many quilts in a year and when you read further find they either only designed them and had their staff actually make them or the quilts they have made are barely 2 ft square. they still count as quilts but do wish they would be more accurate in presentation of the information---more like made this mny queen, this many twin, this many crib,etc... then people wouldnt be wondering how it was done. i dont even count the tops i make for the church group in my personal count for the year as they are tie-knotted and not quilted.