depends .. imagine the NAND flash is broken (which might happens), what you will do then ?
The firmware itself is only one executable, bunch of text files, but within he NAND flash is the whole Linux OS,
manufacturer device driĀ“vers, additional manufacturer aplikations, the factory calibration (which match only your DSO),
the serial number informations and so on.
So did it make sense to have a backup of all these things? You decide ...