I have 14 and think 20 is a solid number with the space I have and the ability to maintain. They all have to be in great shape or you will become a slave to maintaining that number. I have one beater pin. It is my first ever pin so I am never selling it. But wouldn't you know that is the one I spend all my time troubleshooting. Nothing wrong with that if you have time but as your collection gets bigger that can be a lot time.