How many credit cards is too much to affect your credit score?

I am going to ask another question regarding which CC should I add to my credit card profile to add to my rewards. I have excellent credit, pay my balance in full each month, and I use my CC to pay for everything I can to rack up points/miles etc.

I am at a point where I want to increase my points and miles so there are some options. The question is, what is too much. I basically share a VISA with my wife, and have an older VISA that i keep. I realize that you should keep older credit cards for history. I want to add at least one AM/EX either the Starwood points, or the Delta Miles. I also might switch our Cap1 card to the signature to get 2 points for every $1 spent, instead of 1.25 for $1. That is a new card, not a switch. And recently, I have received letters for UNITED miles (20,000 bonus) and AA Miles (21,000 Bonus). I would love to use those just to add to my miles on those flights. Could I add 3-4 cards without hurting my excellent credit? I will not rack up debt.

You could have 50 cards and as long as you kept them in good standing, low utilization, no lates, etc. they won't hurt your scores – you would take small dings for inquiries though.

If you are adding 3-4 cards, and you already have a good card portfolio that has fairly good history, the inquiry dings should be small. After 6 months the inq's will be less of a significance on your scores and at one year they will have no impact at all.

Available credit is not debt.

I can see only one card that you currently have that is probably keeping your scores from actually being higher than they are now. That would be the Cap One card.
Cap One is notorious for not reporting credit limits, they only report high balance – that makes it look like you are over utilizing the account.