Shoot high with your request; They will counter.
My AAoA is the minimum (I think it is 1 year for FICO calculations). CK has me at 3 months AAoA.
I originally only asked for 8k. Instantly approved. 48 hours after approval, I called the automated system and asked for a 20k CLI. The system said the max CLI I was eligible for was 6k. So now I have 14k. If you shoot really high like I did, then the system will give you the max you are able to receive from them.
I've never had any issue getting approved for more Sync Bank cards. My most recent one has been Care Credit and that was two months after getting my $5k Ebates Visa and those $2k CLIs on my other two.