I have a 4 tub rack with 1.5 adults per tub. I do not separate any of them. I tried at first but it seemed to stress them and I ended up with mothers killing babies and males constantly. Mine produce consistently for about 8 months usually at which point they are fed off or frozen. I have been told that they will go longer but I prefer to keep the numbers up and not wait for a drop in production. When it's getting close to time to retire an adult, I pick an unrelated baby from another tub and put it with its new family. I can generally keep up with my rat eating collection. Occasionally I have to thaw a few, occasionally I get to freeze a few.