Wife and I in our forties, she has a CitiBank card (forget whether it's MC or Visa) in her own name, had it for a while, dunno her limit but I believe it's well over $10K.
I have Chase Visa $25K (she is an authorized user on this card), Citibank MC $23,400, Discover $10,400, AmEx Gold is oldest account "Member Since 82," no specified limit, my newest card is the Discover from late 1990s. Balances on these bounce around since neither of us carries much cash, but we pay in full every month so after a major purchase like furniture or airline tickets one of our cards might briefly hit 20% utilization. Now that the car is paid off the only interest we pay is on the mortgage, by the time we get on an airplane we've usually already paid the credit card bill on which the tickets appeared.
Every couple seems to have a designated money nerd, in our case that's me: we make major decisions together and both take part in paying expenses (as we both have salaries), but I'm the one who tracks details and makes sure due dates are not forgotten.
TU 791 02/11/2013, EQ 800 1/29/2011 , EX Plus FAKO 812, EX Vantage Score 955 3/19/2010 wife's EQ 9/23/2009 803
EX always was my highest when we could pull all three
Always remember: big print giveth, small print taketh away
If you dunno what tanstaafl means you must Google it