I was told at AoA on my last 2 trips (2013 & 2015) that they run reports twice a day and put through the charges on those rooms getting close to their limit (I believe they said when they got to be above 75% of the limit) so guests don't have their room charges declined when they're out at the parks. We definitely had that happen on our 2013 trip -- it wasn't a big deal, though. I had gift cards with me so that I didn't have to hold up the line waiting for the cashier to call the resort and get things sorted out.
I usually have gift cards to put towards some of the room charges so I stop at the front desk every day to apply them until they're all used. In 2013, we had 6 people (3 adults, 2 older teens, and one older child) in our suite and no dining plan so we would blow through $500 every two days. When we were there a few weeks ago, I only had a few gift cards to use so I stopped at the front desk on our second day and applied them to the balance. While doing that, I was chatting with the CM and mentioned something about the $500 limit. She told me that it's $1,000 at AoA. I asked her when that started. She said that she had been working there for 4 months and it was always $1,000 since she started. I had reason to stop at the front desk a few days later and asked a different CM what the limit was and she, too, said that it's $1,000 and had been that way for at least 6 months...maybe longer, she couldn't quite remember. When we got our final statement at check-out, I noticed that they put through one charge to our credit card for ~$800 on the 4th day of our stay and then the final day the balance of ~$450 was put through. I don't know if it's $1,000 at all of the Values now or just at AoA because of the suites and having more people in a room.
Still not sure why they have to have different limits at different levels of resort.