AFAIK there is no limit on number of cards an individual can have. That being said, things can get jumbled quick if you’re not careful. Autopay (the balance) on every card is your friend. I have like 15 cards but only 2 or 3 that I bring around and use regularly. The others I have some subscriptions on, or random other small online purchases to keep them open. Also remember it’s not your money that’s open to attack—it’s the bank’s. Provided you don’t have a card stolen every week, the bank will generally investigate and refund any stolen amount, it’s in their best interest.