Half-Life of THC...Metabolites -- 3days.
trufax
http://www.ehow.com/about_5279857_marijuana-effect-metabolism.html
"THC remains in the plasma for at least three days with a half-life of 28 hours, increased to 57 hours for nonusers. "
It's going to depend ... I'll try to research more online. This was the first I found.