#1
i have an acoustic and i recently switched from nylon put a set of phosphor coated steel strings on and they said usually you get around 2 months of life out of them even in the humid climate of orth queensland, ive had them for about three weeks and they feel like rusted fence wire and dont sound much better than rusty fence wire, i only skipped wiping them down after i practised once (i have very sweaty hands) is this typical or am i doing something wrong
#2
Mine usually last about 2 months maybe a bit less, but really it depends how much you play your acoustic.

I play mainly electric so I only play my acoustic 4-6 hours a week give or take, if your doing 3-6 hours a day on your acoustic I could definitely seem them lasting a month. That being said the level of comfort you enjoy with your strings is personal, some people do it 3-4 times a year others I've heard as much as every 2-3 weeks.