Question on time vs cartridge performance. I have a number of high end cartridges (most with no stylus) from the late 70's to mid 80's. Examples are: Pickering XSV3000, ADC XLM Mk II, and Shure RXT4. As they are magnetic, do they significantly deteriorate over time or not. Not sure whether to purchase stylus's for them or just purchase a new cartridge/stylus combo.