I am new to this. I just applied for:

Barclay's US Air
Delta Gold Sky Miles
Chase Marriott Rewards
Citi AAdvantage Visa

Already got approved for Citi card waiting to hear back from others. When should I apply for more cards? And when can I? Whats the most amount of cards you have ever kept open at a time?

Looks like you have overdone it already!

I would research around FT a little and you should find your answers. It all depends on your credit profile, without any specifics it's difficult to help.

I would have done the citi 2 browser trick for the AA cards. It's probably too late now.

Why did I overdo it? I heard many people on here and other sites get like 6 cards. 4 isn't that much

How long do you guys wait in between batches of cards that you get?

Depends what your credit is like to begin with. Personally I'd say stick to 1 new card per 6 months to stay well under the radar and cancel unused ones so your available credit figure doesn't get too high. YMMV. Good luck!

Like I said before, it depends on your individual credit profile. What's you FICO score? How long of credit history do you have? How many current CCs do you have? If everything is in perfect shape 740 FICO (after the inquiries and new accounts report) AND you can meet the spend on all of your cards, people can apply every 90 days or so.

Once points post after you meet minimum spending requirements, do you always have them? Or do you lose them when you cancel card?

My fico score before I applied for 4 cards last night was 740

Too many inquiries in a short period of time hurts your FICO score. Your score is decent, but it will take a hit because of this. However, it will recover in a few months. I would recommend waiting at least 6 months before applying for any more cards.

Generally when points are deposited into a partner program, such as Aadvantage miles or Delta Skymiles, the points are relatively safe when you cancel the credit card. There is a rumor that the credit card company might take back the miles bonus if the card is cancelled after less than 6 months. I recommend keeping the cards open at least 6 months, but it is better for your credit score to keep them open until the annual fee is due, then cancel.

If you have points in a credit card program such as Citi Thank You points, Chase Ultimate Rewards points, or Amex Membership Rewards, remaining points expire when you cancel the card.

I recommend waiting 90 days before you apply for new credit cards. You will get different responses from different people based on their comfort level.