3
I am 20 and on 8/9 credit cards. My bank(who I have 0 through) was super shocked but exactly as you said the rewards are great if you play the game.
25, have had a $500 limit CC for 2 years and I LIVE off it. Gets paid down every month and I been saving hella $$
Rewards cards are the most insidious income redistribution scheme, in a reverse Robin Hood manner