I have a large Aussie, not quite basketball sized which I have had for over a year. It's definitely moody, somedays it's huge and some days it only fills up 1/2 its potential size.
I have an IP elegance and steadily went downhill over a two month period and it was almost dead. I put it in low flow and low light and forgot about it. It is actually coming back. It is growing new polyps. I have had it for a total of about 5 months.