Decreasing your total credit line may be helpful if you seek an online approval of your application. That is, you don't want to interact with a rep to move credit lines around to win that approval. I generally don't reduce my credit lines. Instead, when I close a card, I allow the credit line to disappear. That "makes room" for my next application. Yes, yes, I know that a lower available credit will "hurt" my credit score. I'm unafraid for my 815 FICO going down to 805. Big whoop.

RNE, noting the obvious by pointing out that even if one does monkey around with one's credit line, Chase can nevertheless give an application the boot for many reasons other than credit line concerns.