We have 5 iphone/ipod touches in our house, and all have otterbox cases. Our oldest ipod touch and an iphone 3GS were being handed down to the 5 and 7 year olds as part of their Hanukkah presents. The cases are over 2 years old and do show some wear and tear- the devices are still brand-new looking though.
Anyhow, I originally contacted otterbox when cleaning up the ipod touch about getting a different color silicone cover since the case we had was black/black and I though DS would prefer a brighter color. The silicone was ripping in 2 areas after 3 years of use which is not to be unexpected. Otterbox promptly replaced the entire case free!! Even though well out of warranty.

Fast forward to last night, I took apart my old iphone 3G case to wash it up as it was super grimy (already gave it to DD for Hanukkah) and there was a crack in the hard plastic (no doubt from me or the kids dropping it endlessly over the 2+ years I've had it). I emailed otterbox to see what they could do and voila- new case on the way, free. Even though it was totally years out of warranty.

Awesome CS!! Love Otterbox!