Do I need to run an expand drive sketch if I update the Yun Firmware subsequent to expanding?
After upgrading the firmware and rebooting:


Log in to your Yun through your browser and use the LuCI interface. 
Navigate to "System" > "Software" and observe the "Free space" meter. You will see that the total space shown is between 800KB and 1MB, instead of the size of your flash drive. This indicates that the system is that of the memory available on the board.


Yes, you will need to run the expander sketch again and reinstall software that was previously there. (You might want to back up the contents of the drive beforehand, using a PC running GNU/Linux.)