Further to JW411's post 130, once the new rules came into force, I was advised by my AME that the very low level permitted meant alcohol could be detected over 24 hours after consumption. I changed my habits to not having any alcohol at all on the day before a flight, meaning a drink only on day one of a two-day break. That gave a minimum of some thirty hours. Restricted the social life, but kept me legal. Now I'm teetotal (but no longer flying!)