mammos after mastectomy

I’m a bit confused - can anyone help? I had a mastectomy 18 mths ago with 3 positve nodes removed and have been told by my surgeon that I only need a mammo done every 2 years. My oncologist told me that I would have one every year.
I have a neighbour who had a lumpectomy 9 years ago with no lymph node involvement , who is looked after by the same hospital but a different surgeon and she is still having yearly mammograms.Is there a set protocol or is it down to which surgeon you are under? I’d be really grateful for any info as I am seeing the surgeon for a check in a few weeks. As you all know - it’s so important to know that we’re having the right follow - ups. Thanks

No idea if there is any protocol. A lot of people seem to get yearly mammo’s, but where I am being treated I get one every 18 months. And that is in a centre of excellence.