A 3rd level expert Elf has a normal listen of +6 (+2 Racial, +4 Skill Points). I gave the elf a -4 for sleeping and a -4 for being drunk. Does that sound right? Is there any official rules?
Natural 20's rules for drinking (which seem to work fine in my limited playtesting) gives penalties to checks of -1, -2, -4, -8, and -16. Of course, at the -16 level you have to make balance checks to walk (at -16!) so you're "plastered" at that point.