I am not sure someone has tested the half-life of all the kavalactones, but anecdotally I feel like it is at least 24-48 hours for a complete clearing of all the kava from my system.
In a study of the metabolism of several kava lactones in male rats, it was observed that about one-half of the 400mg/kg dose of dihydrokavain administered was found in the urine in 48 hours. About two-thirds of this was hydroxylated metabolites. The remaining one-third consisted of metabolites formed by the catabolism of the kava lactone and also included hippuric acid. The metabolites of the other kava lactones have also been characterized by analyzing the urine samples from rats.
Interesting. Thanks for the information. I expect that the half-life of some of the kavalactones is part of the explanation for what people call RT in combination with under dosing or week root.