Before 'upgrading' Firmware, you should probably have an idea of what your radio needs to do that it's currently not doing.
If your radio is working fine for you as is, and you don't need things like RX audio leveling, then what's the purpose? If you want to have the latest firmware just to have it, then I'd agree that R 02.09.0001 is about as far up as you'd want to go. Above that requires you to move into CPS2, and then you get into needing SUM subscriptions.
Your biggest upgrade improvement would be to trade up into a 7550e - which actually has better receive sensitivity and some audio enhancements that you'll never get in a plain 7550.