Permanent Monster Familiars

I need more information about Monster Potential. I've been going around collecting 2 of every familiar instead of 3 because of all of the worry-warts in here but I have no idea WHY I'm not collecting 3.

Basically the cards can have potential bonuses, but only the cards used after that particular patch have the option. Register 3 before that and you cannot register another, missing out on the bonus options. This is of course only a problem on the ones you would actually use while training, bossing or farming.