I want to stay away from having to create a binary file. The idea is that anyone can enter their instructions in an Excel file and export the sheet as a CSV file.
Like I said, you should run a test. Create a file that contains more than 512 bytes. Call micros() before and after each read(). Compute the difference, and write it to the serial port. The 1st and the 513th read should take significantly longer than the 2nd, 3rd, etc. reads. Whether that actual time is significant, or not, only you can decide.
One thing you will notice is that parsing and using the text data is going to take significantly longer than reading and using binary data would.
It might be worth the effort to develop a csv to bin converter to create the binary file. Only testing will tell.