Kitchen Aids are great until they break.
One thought is to do what my neighbor does. She buys appliances (such as her Kitchen Aid 600) from Williams & Sonoma because, apparently, if it breaks at any time, they will replace or fix it for free. It's more expensive to buy from them, obviously, but if they'll replace the mixer or fix it every time the KA worm gear or motor breaks (mine has broken twice in ten years), it's not a bad deal. I've never tried this, though, so I can't vouch for it.