I have a Cartridge Keeper with a selection of Cart's ranging from Ceramic, MM, HOMC and LOMC.
I have a few LOMC Cart's still remaining on Tonearms>TT's infrequently used.
I have collected Cart's with a shortish user life for R&D Purposes. These are available to be used in conjunction with owned Cart's by others, from the Same Brand and Same Model. This is for the purpose of A/B Comparison of equipment, where a Cart's change over is not desired during the demonstration, this improves the experience when comparing, when two very closely mimicking Cart's are mounted.
I also have a few Cart's that are destined to be Donor Models for a rebuild design, that I have agreed with Third Party Service Technicians to be undertaken. These are the ones I enjoy the most, there is a lot to be discovered, by bringing a material into use not commonly found in the mainstream today. A skilled Technician also gets fired up and quite creative when the challenge is presented.