No, I don't think it is something that has to be done annually. All affected institutions are updating their records, you could have accounts that pre date any of the money laundering legislation or only have part id from easier rules years ago and they are obliged to ensure they have proper records. I had to do it recently for Avantcard but would have had an MBNA account, whom Avant too over, for many many years and this was the first request like this I got.
If you ignore it there is a risk of account being frozen however if it's just a mortgage then that's unlikely as they are not going to freeze interest being added on or payments going in, a bigger consequence if you have say a current account. They will just have flagged the account as having updated id outstanding more than likely and next time you have any dealings with it you will have to provide the id.