I know this isn't anything 'new', but I just wanted to contribute my Discover CLI details.
I got my card back in July; in October I took them up on a balance transfer offer for $3500, and I'm taking my time paying it down (since I'm also on a new account 0% promo, I don't pay interest on new purchases until July). In November I gave the 'button' a try, and was pleasantly surprised when they gave me a $500 CLI.
I planned to not even bother with the 'button' until the account is PIF this summer, but my curiosity got the best of me, and I gave it a try today... and got another $500. My current balance is around $4k, and I'm making payments of $200-$400 each month but also using it heavily as my 'general spend' card. Again, I plan to have it PIF before the new account promo is over. (I tend to take full advantage of my 0% promos... just a personal preference.)
So, the 'take-away' here is that even if you are carrying a significant balance, if you're paying more than the minimum each month there's still a chance for a SP CLI. Note that my FICO is 715, and is inching up 1-2 points each month as my final 'baddie' is about to age off in a few months. Also note that had they informed me a HP was necessary, I would have declined and simply waited until I get the account PIF, at which time I'm hoping for a more significant increase anyway.
Hope this helps somebody! 
(My initial credit line was $5500, then raised to $6000, then today increased to $6500.)
Congrats on the increase...and thanks for the data point.
Thanks 4 sharing........
Congrats on your CLI's and thank you for sharing !
NFCU Visa 30k | NFCU Platinum 30k | Cap1 QS 12K | Cap1 QS 11.5K | Barclay MC 9k | Delta Gold Amex 30K | Discover IT 14K | CFNA FS 3200 | CareCredit 20k| Paypal Credit 5k |
I appears that I'm on Discover's special alternating 91 day / 31 day program. 
Congrats
