Got my Sams card last year in Oct. CL was $600. I got an Auto CLI in Feb to $900. Just called the customer service line and the rep asked me how much of an increase I was looking for, I told her I wanted a CL of 2k. She took my salary info and came back and said I can give you a $4k increase so my new limit will be $4.9k 
.. .I am floored.
yes I was surprised as was the customer service agent