Build quality is defiantly a priority in my opinion with IEM's. I often forget mine in my pockets and step on my pants, or they'll come loose and smash onto cement. Little things like that are generally why I haven't spent much more than $50 on earbuds thusfar.
My most recent pair, Panasonic RP-HJE120-K, have actually lasted me for a little over a year now, to the point where the paint is coming off. But recently its begun to break off. Been fixing it with superglue (drive is unaffected, talking about the casing), but its nearing its end soon. I think the limit for cheap IEM's is only about a year.
As for sound quality, I am in search of an IEM that specializes in clear vocals, strong bass, and slightly forward mids. Most importantly, not muffled or muddy sounding.
EDIT*
If I can't get good sound quality off the shure's, maybe its better to stick with my panasonic, and replace it ever year or so. I don't want to invest in a breakable, good soundquality IEM either.