I must admit to keeping some letters, one congratulating me on accelerated promotion and another on my result on the ISS course. Both by very senior officers and both unexpected.
My farewell letter OTOH was largely drafted by me as my boss said he would have to draft it for the AOC. When the Air Force was far larger and with more Groups etc the AOC knew who you were.
Now, pro rata, the number of officers serving under an AOC is probably fewer but I bet the AOCs don't know half of them.
At least when we had a meeting at Strike Chris Moran made time to come and visit and meet us all. We only found out later that he had just signed off our bonus recommendations - top bloke - RIP.