There are two scenarios where you might actually want to downgrade to a version of Firmware that pre-dates what shipped in your board.

1. We goofed and released an “improved” firmware that inadvertently introduced a bug. Rest assured, we test every release very thoroughly, but we are also human. Naturally we will fix the bug and release an upgrade very quickly. Meanwhile, the quick work-around will be to downgrade the firmware in your board to a known good version.
2. (The probability of this one is very low, so don’t stress over it!). Your application program is very large and takes up all the available program memory in the version of firmware you developed it on. Then you get shipped a batch of controller boards with “new improved” firmware that takes up more memory. Suddenly your application won’t load into the boards because the amount of available program memory is less (firmware and your SPLatWare both use slices out of the same memory area). The solution for you is to reFlash your boards back to the version of firmware you had when you developed your program. You can also order boards with a given firmware version, though an additional charge and/or minimum order quantity may apply.