Thinning badly with a number 2 on top, I can't imagine I would have a record for very long......... my oldest hair has been there for about 2 weeks!
It does seem to test for more things than I thought, but the motivations for these tests need to be examined. Don't confuse genuine safety aspects with social control. It cannot be disputed that the drug associated with the vast majority of accidents is alcohol, if you want to stop this then have compulsory breathalysers in each airport/ strip. Before you fly you must attend for a breath test or risk revocation of your licence. The pilot flying after a heavy night is of far more risk to himself and others that someone who took MDMA 90 days ago. Read this if you need convincing!
Air Accidents Investigation Branch: Piper PA-28R-201T Turbo Cherokee Arrow III, G-JMTT
Let me add that no, I do not take drugs, no, I am not advocating their use, and no, I do not think they are safe. But, in the piloting community, it is booze that is the problem 99 times out of 100. Crack down on that if anything. 8 hours bottle to throttle is a nonsense when the limit is (rightly) 20mg/dl.