I once had an interesting discussion with a Best Buy store manager about the apparent 1 year cycle on low to mid en consumer electronic. He claimed that Best Buy had a policy to discontinue electronic after one year and move it to a less salable position after 6 month since consumer lost interest. And as a result manufacturer came up with new product to cover this time frame.
That is, new models where often not driven by new technology/features, but rather by consumer interest/buying pattern!