I've relapsed twice after long-term sobriety...once after 6+ years sober (relapse lasted for a year) and once after 7 years sober (relapse lasted for 8 years). Looking back I had abandoned any type of recovery plan and was relying on my own willpower to stay sober. I had reverted to thinking and behaving like an active alcoholic minus the alcohol well before I actually picked up a drink. That was my experience anyway. It might have seemed like everything was fine and the relapse came out of nowhere, but it was what I wasn't doing on a daily basis anymore to treat my alcoholism that led to my relapses.