I'm just keeping the biggest ones. I have already culled most of the runts, variegateds, and misshapen ones. I have two trays which I sowed this past winter, so I've been culling as I go and I will probably keep doing so until I only have a few left.
Many Faucaria (and Lithops) grow faster if they're sown in the middle of winter. I sowed these at that time by chance without realizing that until later.