While everyone has a different profile, I've tried on days 30/31 and 60/61 and a few times in between both statements (on my 2nd). Every time I hit that button, Discover comes back NOT YET, TOO EARLY. I will hit them up on day 90/91 and see if they return any love. Good Luck!
I've hit it on those days stated above and also on the days after my statements cut. You can always try. It's a SP so you have nothing to lose.
Im going to try today and tomorrow then every 30 days 
Ill post back what happens today!
It was a no go...
At this time, we cannot increase your credit line.
However, you can make another request at a future time. You will receive a letter in 3-5 business days that will detail the reasons for this decision.
I will try again maybe next month.
Once I do get a cli im going to try Steve's way and apply once a week
I tried my 1st CLI after 6mo with Discover! SL 3K now it been about 11mo and they gave me $15,500 CLI all in past 5 months all SP
After the 1st 6mo I think you can do CLI every 31days.
@glamchick wrote:It was a no go...
At this time, we cannot increase your credit line.
However, you can make another request at a future time. You will receive a letter in 3-5 business days that will detail the reasons for this decision.
I will try again maybe next month.
Once I do get a cli im going to try Steve's way and apply once a week
Figures! Same dreadful message I have been getting. When you get the letter, it'll say "not enough time with Discover CL" or something like that...which basically mean too soon.
Thanks for the responses
Im worried that they will not give me a CL due to some school loan lates on my CR fromf 3 years ago. My TU score is 725 right now.
Will see what happens next time.