I am about to pass the two year mark on my salvage radiation. I had no issues with ED after the surgery and my radiologist felt I would not have any trouble after the radiation. I think my age and current function at the time is what drove that statement from him.
With that said I did experience some issues about 1 year out but things seem to have returned to pre radiation status over the past few months. I have read that the two year mark is the best toll gate on ED status as the radiation continues to work for that period and your body will fully recover over that period.
Hopefully you will see improvement soon.