I think that greatness of the cartridge will be evident from few first hours. Whether its great everyday cartridge it is a different matter. Great piece of art or sound of Stradivarius violin will impress you from very first minutes. Many cartridges are doing 2-3-4 things exceptionally well or they best suited for some music stile and content. Some cartridges are well balanced, but don't shine on anything is particular. We call them "neural", I guess. They are great, but they are not touching our feelings as deeply as more "specialized" cartridges during their glory moments. I stopped long ago to treat cartridges as do-it-all devices, but as musical instruments. Every one has its own strengths, weaknesses, "preferences" and time-to-boredom factor. Some trend is shaping up: MCs and IM for jazz, acoustic music and classics, MM for rock-n-roll.