For me I'm lucky as I have rather dry hands... some people have naturally moist hands and that's why there are a lot of coated strings on the market. But I also keep my guitars in their cases when I'm not playing them for long periods of time, and I also wipe my strings often and especially after playing them. Also, I keep my room's windows closed during and just after rainfall so the humidity in my room doesn't skyrocket too quickly. I can actually feel the humidity change and it will definitely kill your strings real quick. For me I don't use coated strings, just regular Ernie Ball Slinkies and Earthwoods, my strings last pretty long and I do tend to delay changing them as I do like the sound of slightly-dead strings.