We have been raiding with our current loot system over a year now. We want to change our decay system and I do not see an area that lets me change the values I want to change. Currently we have our decay set to start decaying 30 days after the values are input. The next 30 days the value goes from 100% to a base value of 25%. This is the value I want to change. I want to be able to have our decay start after 21 days, and decay to a zero value over the next 49 days. I do not want the decay to stop at 25%. How do I change this?

You can change your decay configuration at Admin > DKP > Loot Systems, however, you need to have full administrative privileges for access to this section (due to the destructive power of this section - being able to delete all the DKP in a minute or two).

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It's all in the reflexes.