Model 12 Featherweight|Winchester Shotguns|Forum|Winchester Collector

I have become rather enamored buy these guns and have three of them at this time.  They really seem perfect to me and are even a pleasure to shoot clays with if using 7/8 and 1 ounce loads, which are easier to find these days.  My question is why the short life span?  I have read they all were made between March of 1958 and March of 1959 and then sold through ~1963.  I have owned hundreds of shotguns over 40 some years and this one seems near perfect.