I have 11 credit, and 2 debits (plus countless other random non debit ATM cards from various credit unions I've joined throughout the years).
Amex x3
BPPR x3
Santander Puerto Rico x1
Barclaycard x1
GECRB x2
Discover x1
Citi x1
Ally x1
Out of these, Amex green, my Discover, and my BPPR debit live in my wallet. Any other card is on an as-needed basis.
ie- if I'm flying B6, I'll bring my Santander Jetblue MC, if I'm on AA, I'll bring my BPPR AA card, or if I need to impress, I'll bring my Amex platinum.
The Ally debit card strictly there for mainland US travel, in case a mainland US atm tries to rip me off from my BPPR card (which many ATM's don't recognize as a US card)