you can do one every 30 day and those vary. But usally any limit increase after 3-6 months between each other is higher in limit.
for me, my crystal ball was correct, 3mo on the nose. i got a disco cli today, and i got the doubledip!!!
i last got one on august 3 and today is dec 3. and when i first got my disco card they told me 3mo is the most usual time in between, so 3 is the magic number. look at all these 3's. they even gave me $300 before i double dipped it.