I haven't read much SPN fanfic, mainly because I'm interested mostly in Sam fic and that usually means limp!Sam (a term that DRIVES ME BONZO AND MAKES ME WANT TO SICK EVIL!KICKBUTT!SAM ON THEIR BEHINDS), but in every last one of the pre-show fics I've read, John was an alcoholic who ran away and got drunk when his boys were in trouble/hurt/dying/whatever. Which, IMO, is absolutely ridiculous. But hey, it makes for some great cuddle time between Sam and Dean as they try to soldier on and survive all by themselves... *rolls eyes*