Data Point: Opened my first US Airways (and Barclays card) on 9/14 with instant approval $15K. Sent a message to halve that line 2 weeks ago. Applied today using my own referral link sent to a different email address with the first card still open and was instantly approved for $12.5K. Will see if I get the referral credit and I'm doing the 3 month challenge now on the first card but I guess Barclays likes me and opening another card after a little more than 4 months is possible.