My Klipsch S5i lasted 2 years, and I'm a durability testing machine for IEM's. I'm talking about two years of getting plugged in and out of my iPhone multiple times a day, everyday. 2 years of getting rolled into a ball and stuffed into a pocket in my jacket, then getting untangled later to use again - multiple times a day.
After two years, my S5i's jack finally gave out. I bought a replacement jack for it and will do the soldering soon, but for the meantime I'm really enjoying my VSonic GR07 despite not having a mic and iPhone controls.
The Klipsch S4i is supposedly not as rugged as the S5i, but is also cheaper. Shure and Sennheiser also have IEM's that have a mic and iPhone controls.
I'm sure this has already been mentioned somewhere in this thread, but the forums on head-fi.org is the place to go for research on this topic. I'm pretty happy with my "entry level" items:
Audio Technica ATH-M50
I plan to add the Grado SR325is and Shure SE215 in the future. I also want the Ultrasone Edition 8, but I have other more important expenses to deal with first LOL
Klipsch are awesome... the sound reproduction is unparralled for the price u pay.. you can always get better, ,but for the price, they will rock your socks off