The decay model I have got works fairly well and have set the DKP to not got below 0.25. However, I have noticed that the DKP for my guildies is going into negative figures and it's that the DKP is decaying into negative, not the fact the DKP is being spent.
DKP can still go negative with Decay enabled. The 0.25 means that each point itself becomes worth 25% of it's original value. Both Earned and Spent points decay. So, for example, if JoeBlow had earned 100 points and spent 200 points 6 months ago (and for the sake of easy math has not raided since then). Those points would be fully decayed, being so old.
So, when earned (that is, undecayed), those points would be:
100 - 200 = -100 points
However, decayed (At 25% of their points), JoeBlow would be at:
