> Where is the limit?

You lose roughly ~0.75 lbs of body fat at normal fasting levels assuming a reasonably active regular sized person. So how ever many days worth of body fat you would like to gain and lose regularly. You would have to eat back the same amount and probably wouldn't want to gorge yourself too much. A reasonable practical limit might be 5 days.

All of that assumes that you want to maintain a set weight. So the real limit is how much you want to eat in a single sitting. Take those calories and average them across as many days as needed to maintain weight.