Like with other tech, they tend to keep on working just fine, but you want to replace them because the new model has better features. I upgraded from the 910 t

Like with other tech, they tend to keep on working just fine, but you want to replace them because the new model has better features. I upgraded from the 910 to the 920 to get the Bluetooth upload. That said, I'm not particularly tempted by the 935 over the 920, and I know people still using the 310XT which was released in 2009...