you HAVE to wipe your strings down (clean cloth works fine) and ALL the metal parts of the guitar after gigs. if you don't, corrosion sets in very quickly.
i go thru lots of strings as i play out from 1 to 4 gigs a week. i use EB strings (regular 10's) and tend to get maybe 2 gigs from a set. they seem to not break as often now that i'm using 10's instead of 9's. my tone seems to have improved a little with a thicker string set as well.
my hands emit an extremely acidic sweat that eats the strings and metal parts rather quickly if i don't wipe down everything after every show. if i keep my hands clean and wipe everything down regularly, i don't have any problems and am able to get a couple shows per set of strings.
considering the wear and tear my strings go thru (especially on my trem guitars), i won't ever let them go past two shows per set. strings can only take so much stretching and bending before they break. i always bring back up guitars for just that reason - especially my trem guitars.
we should be happy that we get away with such cheap replacements for guitars. i watch kids buy reeds like crazy for their wind instruments and they can get very expensive (oboe and basson reeds cost around $8-$9 EACH!).
i don't think the smoke adversly affects the strings but does make everything stink. i pulled my pedal board out the other day and it almost knocked me over from the smokey stench from bars - and i'm a smoker!
i keep my stuff in a non-smoking room but i can't do anything about the bar stench attatching itself to my gear besides covering things up with a blanket for gigs that are more than a one nighter.
just my two cents