Originally posted in the Blog of Meenkie Bladedancer (Lindblum) http://lodestone.finalfantasyxiv.com/rc/diary/entry?e=167551
Community name “Gathering Fatigue”
“To clear up your questions, we have checked with the Dev. team and found out the following.
As a countermeasure against RMT activities, the probability of gaining items through gathering will start to decrease after repeated attempts over a long period of time. After a certain number of attempts, items will no longer be obtainable through gathering.
To explain a little more on what goes on behind the scenes, there is an internal counter which measures how often a player has attempted gathering activities. Players will start with a maximum pool of 2,500, which will decrease by 10 each time a gathering attempt is successful and yields an item. Once this number decreases to 1,000, players will find it harder to obtain items. At 0, items can no longer be obtained through gathering.
Stopping gathering for some time will bump this number back up. The recovery rate is currently set at 100 per hour.”
150 succesful attempts before you will see a reduction. 250 succesful attempts maximum. Regen at 10 successes per hour.