Murray is right about the instruments responding differently, but Andres' remark about sweating made me realize that climate can be a big factor also. I live in a hot, humid place (Fla.) and my nylon strings all wanna turn to rubber and my steel strings all wanna rust. My Thomastiks last about 4 weeks, even six in a pinch, but I wipe them down with a cloth after I'm finished playing. Truth is, I prefer steel strings after they have been on a guitar long enought to lose that fresh trebly sound, but still have the longest sustain possible.

John Pearse was my choice before I found a Thom/Inf. dealer. Frank i.t.s.