I've never had mine deleted. They did seem to add my middle initial after my first name once. I corrected it and it hasn't changed since. Note that the information is stored with each flight itin. If you have any existing reservations, I would check them under My Trips at the "Provide TSA Secure Flight Information" link.
I still can't get rid of my middle initial in my first name line. I've changed it a few times but it always goes back in after a couple trips.