Just got through chatting with a very helpful representative from Citi. I requested an APR reduction (got 18.99% down to 16.99%). I also asked a few questions regarding how frequent such a request can be made (if any policy is in place), and was told that I could request further reductions at any time, and they will simply check if any better offers are available. I then inquired about product changes, and they promptly recommended the Dividend and Thank You lines based on my inquiry about standard cash back / rewards versus the Citi Easy Deals that the Diamond Preferred card has. Sadly, all PC requests must be completed over the phone (boo!) unlike my recent Discover experience. As far as CLI requests, I was told that they no longer have a policy as far as he knows, but it used to be 6 months between considerations after an approved CLI. So now I know to check back frequently regarding APR reductions, and that, depending on how my credit changes, there is no fixed time between CLI's as I just received my first increase from them at the start of the month.
On to Capital One next? Perhaps! 
EDIT: Contacted Capital One, and the best they could do was 9.99% for 7 months, then back to my standard Prime + 10.65% (13.9%). As I have 0% for the next 14 months on another card(s), I declined.
:::: FICO scores: EX: 747 (7/25/14) ::: EQ: 766 (7/25/14) ::: TU: 761 (7/22/14)
@SamsungHDTV wrote:How do you use your citi card? PIF or carry balance? Just curious.
I had carried a balance for a while, but have now paid in full and will continue to attempt to do so. However, I've added my sister as an authorized user to help her build some credit history (if it even works), so depending on whether she has to use it or not, it may carry a balance occasionally. I'm just trying to get my APR's reduced for any future needs that may arise.
@tinn wrote:I just finished an online chat with Citi and I got my APR lowered on my Diamond Preferred from 17.99% to 15.99% !!!! This Forum is full of great information.
Congratulations! I never would have known that it could be that easy to do without reading the forums here. Maybe in a few months we can knock another 2% off? 
I'm glad I could help somebody else the way other posts have helped me! My recent barrage of new accounts didn't get the most favorable terms, so after I build up a bit of a history on them, I'll have to try to talk their APR's down as well. If you don't carry a balance, it doesn't matter what the APR is, but I'd rather be safe than sorry, in the event that I have to carry a balance on one or more cards down the road.
@keithB wrote:
@ticalc2014 wrote:I'm glad I could help somebody else the way other posts have helped me! My recent barrage of new accounts didn't get the most favorable terms, so after I build up a bit of a history on them, I'll have to try to talk their APR's down as well. If you don't carry a balance, it doesn't matter what the APR is, but I'd rather be safe than sorry, in the event that I have to carry a balance on one or more cards down the road.
How long did you have the card before hitting them up for a reduction in APR?
I have had the card for 2 1/2 years. I wish I had known in the past that it was this easy to request an APR reduction, but I didn't really pay much attention to the terms on my cards until I signed up here. Also, my credit hasn't really improved until the past month or so, from the time that I opened the account, so I'm not sure what kind of offer I would have gotten solely based on my history with them, or what factors they take into account when processing an APR reduction request.