UPDATE: The photo of the cracked insinkerator that I originally linked to is now down, as are a lot of photos. Has someone been grooming their image on the web?
UPDATE: It literally takes ten minutes to swap out the disposal if you replace it with the same model. So although the Insinkerater "badger" tends to crack after a number of years, it was far easier to replace it with the same make and model unit. If I changed disposal brands, I would have to spend more money and time re-configuring the plumbing. Or, if I just plumbed a regular drain, I would have had to spend more time and some money on plumbing parts - and again it would be weird to have a switch for a disposal and no disposal.
UPDATE: After removing the Insinkerator, which was a Badger Model 5 (1/2 HP) I noticed there are actually THREE CRACKS in the device. What could cause this sort of cracking? My theories are this:
1. Bad plastic that is degrading over time, perhaps aided and abetted by the use of chlorine type cleaners or other chemicals.
2. Clogs to the machine being cleared with a broom stick (as they taught us in the Boy Scout Manual) causes pressure to the inside of the plastic housing, which can later lead to cracks.
3. The weight of the motor causing stress to the plastic, resulting in cracks.
Given #3, I am thinking that perhaps the 1/3 HP model might last longer, ironically, as the motor is lighter. This thing is heavy, and that is a lot of weight to hang off the plumbing. Plus, it's $78 instead of $99. Cheaper is better, particularly for something we rarely use.