We managed to get 5 years of coverage for a very good price which made it worth while. Here in and around Austin the roads have a lot of debris on them (people in pickup trucks do not seem to care what falls off them) and it is very easy to damage both tires and rims.
I would guess it depends on where you live and how much you drive. If you live in an area with relatively clean roads and no pot holes, you would be safe in not getting the insurance. I have had 4 tires in the last 5 years damaged by nails and screws to the point where they needed replacing and the insurance picked up the cost of the new tire and balancing. The cost to replace those tires alone (had I paid for them myself) exceeded the cost of the insurance I paid.