Answer to your first sentence: as many as you need. There is no magic number or range like there is with utilization. In my line of work I have seen guys with 830 FICOs that have 3 cards and I have seen 830 FICOs with those who have 20 cards.
Wallet: JP Morgan Select Visa Signature $9000 | Chase Sapphire Preferred $5000 | Chase Freedom Visa $2000 | Barclaycard Visa $3000 | Discover More $1500 | Capital One Platinum Mastercard $750 | Bank of America Cash Rewards Visa $500 | Walmart Store $950 | Amazon Store $5000 | AMEX Zync (AU) NPSL | Chase Total Checking | RIP: First Premier Mastercard
