yes it does have a 2-3 day half life (according to wikipedia at least). Note that half life means that half of it is still there, so you can still test positive after several half-lives. 1 half life you have 50% in your system, 2 half lives you have 25%, 3 you have 12.5%, 4 you have 6.5% etc... so depending on the quantity and the sensitivity of the test, you could test positive for a long time (4 half lives is 4-6 days).