As with any wallet, keep your everyday carry consistent. Leather and elastic will stretch to the number of cards you normally carry.
For example: if you normally carry six cards, your wallet with adjust to carry six cards. If you add a few cards to the mix for a total of eight, your wallet will stretch to carry eight cards. If you later remove a few cards for a total of six again, it may not hold everything as securely as before. Just be sure to keep your everyday carry consistent and you should be fine.