If you have already exceeded your first 3 or so then there would most likely not be a bump in score for anymore being added but a ding, this ding can possibly be being overidden by your utilization rate dropping as each cards CL is added to overall util. Most dings to Fico for new accounts last up to 6 months and the points are recovered over that period of time. If your AAoA is already low there would not be a hit due to it falling even further.
It all depends on what's on your file. If you had a very thin file, then you would see a jump. If you had a decent file and the new accounts decreased your AAoA significantly, you'd see a bit of a drop. I don't worry about that, you need a good healthy thick file for your scores to grow. Congrats!
July 2013 score: EQ FICO 819, TU08 778, EX "806 lender pull 07/26/2013
Goal Score: All Scores 760+, Newest goal 800+
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Current scores after adding $81K in CLs and 2 new cars since July 2013
EQ:809 TU 777 EX 790 Now it's just garden time!
June 2017 update: All scores over 820, just pure gardening now.