Thought I would try the 4 month CLI and received a denial via email. "We are sorry we cannot grant your request at this time" reason: "There has been a recent increase in your credit line" ( Last one was in Aug 3, 2011) It also says, since six months is generally the minimum time period, for an increase, please contact us after February 2, 2012 and we will re consider your request. No hard was pulled. Oh well...... Card is Citi Diamond. Was always given one every 4 months until now. As usual, YMMV