Yes, agreed, on the one occasion I did return with proof, I got the impression they could not care less. Year prior, they forgot to tell me so I didn't. This year, as I was up against the wall due to dopey HMPO UK pushing me up against a wall, I engaged an agent and it was not mentioned.
Beware NOT keeping the balances stipulated though... I suspect an Extension could be cancelled if you really got them annoyed.